The Waterproof Bag Spec Sheet: 22 Fields to Fill In

What a Filled Spec Sheet Removes From the Sampling Round

A technical specification sheet is the difference between a quotation and a guess. With the sheet filled, a supplier can price fabric, tooling and labour against named values and can build the sample to a defined target. Without it, the supplier fills the gaps with defaults, and the sample that comes back is a supplier's product rather than the buyer's product.

The cost of a gap is not the gap itself, it is the round trip. An unspecified fold count on a roll-top closure becomes a question, the question becomes an email, the email becomes a day, and three such gaps turn a 6-10 working day sampling window into two weeks. Filling the sheet costs an afternoon and removes that entirely.

The sheet also governs what happens much later. The same values that guide the sample become the acceptance criteria at pre-shipment inspection, and the same document is what a marketplace or a procurement buyer asks to see when they want to know what they bought. A sheet written only for sampling is a wasted asset.

• Every empty field becomes a question during sampling and a revision after it.
• Unspecified values get replaced by supplier defaults, and the sample stops being your product.
• The same values become the inspection acceptance criteria months later.
• A sheet with units is quotable, testable and inspectable; a sheet without units is none of those.

Fabric Block: Denier, Coating GSM and Hydrostatic Head

The fabric block is the most frequently under-specified part of a waterproof bag sheet, because buyers write a denier and stop. Denier describes yarn thickness, not performance. A 420 D shell with a heavy coating can outperform a 600 D shell with a light one, so the coating weight in grams per square metre and the hydrostatic head in millimetres both have to sit next to the denier.

Hydrostatic head is measured to ISO 811 or AATCC 127, and the two are not identical in procedure, so the method has to be named alongside the value. JIS L 1092 is a third method encountered with Asian supply chains. A figure quoted without its method is not comparable, and a figure quoted without a pass definition, usually the third penetrating drop, is not testable. The mechanics of the pressure test are set out in the ISO 811 hydrostatic pressure reference, which is worth reading before you choose a target number.

Coating chemistry belongs here too, because it governs service life rather than initial performance. A polyurethane coating and a thermoplastic polyurethane coating of the same weight behave very differently under humidity and heat, and a buyer who specifies only the weight will get whichever is cheaper that week. Naming the chemistry is the cheapest insurance in the document.

• Denier alone is not a performance value; pair it with coating weight and hydrostatic head.
• Name the test method next to the hydrostatic head value, because ISO 811, AATCC 127 and JIS L 1092 differ in procedure.
• State the pass definition, normally the third penetrating drop.
• Specify the coating chemistry, because it governs service life rather than day-one performance.

Construction Block: Weld Type, Allowance and Tape Width

Construction describes how the shell is joined, and it is the block most often left to the supplier by default. That is a mistake, because the join is where waterproof bags fail. The three decisions are whether a seam is welded or stitched, how much material overlaps at the join, and what width of tape covers a stitched seam.

Radio frequency welding and hot wedge welding produce different edge characteristics and suit different coating chemistries. Naming the process is less important than naming the outcome: a minimum weld width in millimetres, a seam strength value, and a leak check result. ASTM D751 covers coated fabric properties including seam strength, and it gives a shared vocabulary for the number.

Where a seam is stitched, tape width and the stitching window decide whether the tape actually seals the needle holes. A tape narrower than the needle hole band leaves a leak path along the edge of the tape, and that failure is invisible on a visual inspection and obvious in a spray test. State the tape width and require the seam to be verified rather than eyeballed.

• Welded or stitched, per seam, not globally for the whole bag.
• Minimum weld width in millimetres, plus a seam strength value.
• Tape width and stitch window on every stitched seam, verified rather than visually checked.
• Seam allowance at the join, because a narrow allowance reduces the load the seam can carry.

Closure Block: Roll-Top Cycles, Zipper Class and Hardware

The closure is the part the customer operates, and it is the part most often missing from a specification sheet. A roll-top closure needs a fold count and a resulting sealing length; a zip closure needs a class, a gauge, a puller type and whether it is a water resistant or a water-proofing construction. Without those, the sample will carry whatever the line has on the shelf.

Fold count is the specific value that gets missed. Three folds and five folds on the same shell produce two different sealing performances, and the difference is large enough to move an immersion result. Write the fold count, and write it in the hangtag copy too, because the customer will not know it otherwise and will report a leak that is really a misuse.

Hardware needs codes rather than descriptions. A buckle described as black 25 mm side release can be supplied from a dozen moulds with different strength and different finish. Naming the supplier code, or approving a physical reference and holding it, is what keeps a reorder identical to the original build.

• Roll-top: fold count and resulting sealing length, in millimetres.
• Zipper: class, gauge, puller type, and whether water resistant or sealing construction.
• Buckles and hardware: named codes or an approved physical reference, not a description.
• Webbing: width, material and a tensile value where it carries load.

Dimensions Block: Tolerance, Volume Method and Load Points

Dimensions on a bag sheet need three things that buyers rarely write: a tolerance, a volume measurement method, and the load points. A dimension without a tolerance is unenforceable in inspection, and a capacity figure without a method is uncomparable between suppliers.

Capacity in litres is the classic source of argument. One supplier measures to the roll-top collar, another measures to the folded-down mouth, another packs the bag with beads and measures displacement. All three produce defensible numbers that differ by twenty percent. State which method applies, and the figure becomes a specification rather than a marketing claim.

Load points are the structural counterpart. Where the straps attach, what the base carries and what the handle is expected to lift are all decisions that determine whether the bag survives its payload. A 30 litre bag specified to carry eight kilograms and the same bag specified to carry two are different products with different reinforcement.

• Every dimension carries a tolerance, normally in millimetres, so inspection has something to measure against.
• State the volume method: to the collar, to the folded mouth, or by displacement.
• Name the design payload in kilograms and where it bears on the body.
• Specify reinforcement zones separately from the general body fabric.

Branding Block: Logo Method, Placement and Colour Reference

The branding block is short and it is the block most likely to invalidate a photograph. Logo method, placement coordinates and colour reference should all be stated, because a logo applied by heat transfer, by screen print or by embroidery changes the surface it sits on and, in the case of a coated shell, can change the local water behaviour.

Placement should be given as a measured location from a named reference edge, not as a sketch alone. A sketch is interpreted, and interpretation varies by operator; a measurement is not. Where a logo sits across a weld or near a seam edge, say so explicitly, because that placement needs a different application sequence.

Colour reference means a named system and a code. A brand colour described as charcoal will be matched differently by different people, while a stated code with a stated tolerance can be approved once and reused on every reorder. Without it, every run is a fresh negotiation.

• Logo method, and whether it sits on a coated face or across a weld.
• Placement as a measured distance from a named edge, not a sketch alone.
• Colour system and code, with an acceptable difference tolerance.
• Artwork supplied in vector format with fonts converted to outlines.

Testing Block: Method, Sample Size and Acceptance Criteria

The testing block is what makes the rest of the sheet enforceable. It names the method for each property, the number of units or coupons to be tested, and the pass bar. Without a sample size and a bar, a test result is an opinion; with them it is an acceptance criterion that can be applied at pre-shipment inspection.

Water ingress is the obvious entry and it needs to be split. The shell is verified by hydrostatic head to ISO 811, the finished surface by spray to AATCC 22, and the closed bag by an immersion reference to IEC 60529 with a stated depth and duration. Three different methods, three different numbers, and none of them substitutes for another. The full method list and what each one actually measures is on the waterproof standards page.

Acceptance at shipment is separate from type testing and runs on a sampling plan. Our pre-shipment inspection uses AQL 2.5 under ISO 2859-1, which sets the sample size for a given lot and the accept and reject counts. Type testing proves the design; AQL inspection proves the lot. Confusing the two is how a good design ships in a bad batch.

• One row per property: method, sample size, pass bar, and who pays for a retest.
• Shell, surface and closed bag are three separate tests, not one.
• State depth and duration for any immersion reference, never a bare grade.
• Keep lot acceptance on ISO 2859-1 at AQL 2.5 separate from design type testing.

Packaging Block: Polybag, Carton Count and Marking

Packaging is specified last and discovered too late. Polybag type and print, units per carton, carton dimensions and marking scheme all affect freight cost, warehouse handling and the unboxing experience, and all of them are decided before the production slot rather than after it.

Carton count is the value that surprises buyers, because it is constrained by product volume and by carton strength rather than by preference. A bulky dry bag may fit twelve per carton where a flat pouch fits sixty, and that difference shows up in landed cost per unit more than most material decisions do.

Marking should include the SKU code, the colourway name and the carton sequence, because a warehouse receiving two thousand units needs to identify a colourway without opening a box. Where a destination market requires specific wording on the polybag, that belongs here as well and should be approved before artwork goes to print.

• Polybag material, thickness and any required safety or recycling print.
• Units per carton, carton dimensions and gross weight.
• Marking scheme: SKU, colourway name, carton sequence number.
• Destination market wording and barcode placement, approved before the print run.

Spec Sheet Field Table With Units and Typical Values

These are the 22 fields, grouped by block, with the unit each one carries and the value range we normally quote. A buyer can use this as the working template; every field should be filled or explicitly marked as supplier default.

Note that nearly every field carries a unit. That is deliberate: a number without a unit cannot be quoted, cannot be tested and cannot be inspected, and it is the single most common defect in specification sheets we receive.

Two further notes on using the template. Fill every field or explicitly mark it as supplier default, because a blank field is read as an invitation rather than as a decision. And send the sheet once, complete, rather than in pieces: values that arrive in three separate emails are transcribed three separate times, and the transcription is where most specification errors are born.

Tolerance Stack: Where Small Errors Compound

Individual tolerances look harmless and they add up. A body panel cut two millimetres long, a seam allowance one millimetre narrow and a weld one millimetre off centre produce a finished bag several millimetres out of shape, and on a roll-top closure that error shows up as a mouth that no longer rolls flat.

The places where the stack matters are the closure mouth, the strap roots and the base panel. The mouth is the one that produces a functional failure: if the roll-top mouth is not parallel after assembly, the folds do not compress evenly and the seal leaks at one corner. That is a tolerance problem presenting as a waterproofing problem.

The remedy is to specify tolerances where they matter and to leave them loose where they do not. Tolerance on a decorative panel costs money and saves nothing; tolerance on the roll-top mouth costs little and prevents the most expensive class of failure in the product. The sheet should say which is which.

• Tight tolerance at the closure mouth: uneven folds leak at a corner and look like a fabric failure.
• Tight tolerance at strap roots: an off-centre root concentrates load on one side of the seam.
• Loose tolerance on decorative panels: precision there costs money and prevents nothing.
• Specify which dimensions carry tight tolerance, rather than applying one tolerance globally.

Version Control: Revision Letters and Sample Retention

A specification sheet that is not version controlled stops being a specification and becomes a conversation. The discipline is simple and it saves weeks: every issue carries a revision letter, every change is listed in a change line, and the sample built to each revision is retained and labelled.

The reason this matters is that production is booked against a revision, not against a conversation. When a buyer approves revision C and the line builds to it, there is no ambiguity about which closure or which webbing was agreed. Without a revision letter, an approval is an email thread and a dispute is a matter of interpretation.

Retention pairs with version control. Keep the approved sample for each revision, labelled with its letter and its date, and the sheet becomes verifiable months later when a reorder or a claim arrives. We retain the approved build sample for the life of the programme for exactly this reason.

• Issue every sheet with a revision letter and a one-line change note.
• Book production against a revision letter, never against an email thread.
• Retain and label the sample built to each revision, with date and letter.
• Mark superseded revisions clearly so an old file cannot be quoted by mistake.

Common Spec Gaps That Cause a Second Sampling Round

Second sampling rounds have a short list of causes, and almost all of them are missing fields rather than bad decisions. These are the gaps we see most often, in the order they most often appear.

1. Fold count on a roll-top closure left unstated, so the sample seals differently from the intent.
2. Hydrostatic head quoted without a method, so the result cannot be compared or verified.
3. Colour stated as a name rather than a code, so the match is a matter of opinion.
4. Hardware described rather than coded, so a reorder arrives with different fittings.
5. Volume quoted without a measurement method, so the capacity claim cannot be defended.
6. Seam type left to supplier default, so a welded expectation arrives stitched and taped.
7. Packaging decided after the production slot, which adds time to a 35-50 day calendar.

None of these is a hard problem. All of them cost a round trip, and a round trip at sampling stage costs more calendar time than the rest of the programme put together, because everything downstream waits on it.

How to Send the Sheet: File Formats and Handoff

Send the sheet as an editable document rather than as a PDF, so values can be transferred into the build record without re-typing, and send artwork as vector files with fonts converted to outlines. A flat image of a specification is the most common cause of transcription error.

Where a drawing exists, send it with dimensions called out rather than scaled. A scaled drawing invites the recipient to measure it, and a measured drawing is only as accurate as the measurement. Where the buyer has only a reference sample, send the sample; a physical reference answers questions a sheet cannot.

The handoff closes with a confirmation of what was received. We return the sheet with our reading of every field, including the values we intend to use where a field was left open. That returned document is what the sample is built to, and it is the point at which a specification becomes a shared one.

Send the completed waterproof bag technical specification sheet to our team or to service@junyuanbags.com, and reach us on WhatsApp at +86 177 5002 0688. QUANZHOU JUNYUAN BAGS has issued specification-controlled waterproof bag programmes since 2014, with the founding team in the trade since 2004, and the finished sheet is the same document used at pre-shipment inspection under ISO 2859-1 at AQL 2.5.

Frequently Asked Questions

Q1: How many fields does a waterproof bag spec sheet need?

A: Twenty-two, grouped into seven blocks: fabric, construction, closure, dimensions, branding, testing and packaging. Each field should carry a unit, because a value without a unit cannot be quoted, tested or inspected. Filling the sheet costs an afternoon and removes most of the questions that extend a sampling round.

Q2: Is denier enough to specify a waterproof shell?

A: No. Denier describes yarn thickness, not performance, so it has to sit next to coating weight in grams per square metre and hydrostatic head in millimetres. A 420 D shell with a heavy coating can outperform a 600 D shell with a light one, and coating chemistry governs service life rather than day-one performance.

Q3: Which hydrostatic head test method should I name?

A: Name whichever method your market recognises, because ISO 811, AATCC 127 and JIS L 1092 differ in procedure and a figure quoted without a method is not comparable. Also state the pass definition, normally the third penetrating drop, so the result is testable rather than interpretive.

Q4: Why does fold count matter on a roll-top closure?

A: Because three folds and five folds on the same shell produce two different sealing performances, and the difference is large enough to move an immersion result. Writing the fold count into the sheet and into the hangtag copy prevents both a sampling surprise and a class of misuse complaints from owners who fold twice.

Q5: Should I specify seam type or leave it to the supplier?

A: Specify it, per seam rather than globally. The join is where waterproof bags fail, and leaving it open means the sample arrives with welded construction where you expected it and stitched-and-taped where you did not, or the reverse. Naming the outcome matters more than naming the process.

Q6: How do I make a capacity figure defensible?

A: State the measurement method. One supplier measures to the roll-top collar, another to the folded-down mouth, another uses bead displacement, and all three produce defensible numbers that can differ by around twenty percent. With a method named, the figure becomes a specification instead of a marketing claim.

Q7: What is AQL 2.5 and how does it relate to type testing?

A: AQL 2.5 under ISO 2859-1 is a lot acceptance sampling plan that sets the sample size for a given lot and the accept and reject counts. Type testing proves the design; AQL inspection proves the lot. Confusing them is how a good design ships inside a bad batch.

Q8: Why do I need revision letters on a specification sheet?

A: Production is booked against a revision, not against a conversation. When a buyer approves revision C and the line builds to it, there is no ambiguity about which closure or webbing was agreed. Without a revision letter an approval is an email thread and any later dispute becomes a matter of interpretation.

Q9: What tolerance should I put on bag dimensions?

A: Put tight tolerance where the stack matters and loose tolerance where it does not. The closure mouth and the strap roots are where small errors become functional failures; decorative panels are where precision costs money and prevents nothing. State which dimensions carry which tolerance.

Q10: What is the most common gap that causes a second sampling round?

A: An unstated fold count on a roll-top closure, closely followed by a hydrostatic head quoted without a method and a colour given as a name rather than a code. None is a hard problem, but each costs a round trip, and a round trip at sampling stage delays everything downstream.

Q11: Should hardware be described or coded?

A: Coded. A buckle described as a black 25 mm side release can be supplied from a dozen moulds with different strength and finish, so naming the supplier code or approving and holding a physical reference is what keeps a reorder identical to the original build.

Q12: What file format should I send the spec sheet in?

A: Send an editable document rather than a PDF so values transfer into the build record without re-typing, and send artwork as vector files with fonts converted to outlines. Where a drawing exists, call out dimensions rather than relying on scale, because a measured drawing is only as accurate as the measurement.

Q13: Do I need to retain the approved sample?

A: Yes, and label it with its revision letter and date. The retained sample is what makes a reorder verifiable months later and what settles a claim quickly. We retain the approved build sample for the life of the programme for exactly that reason.

Q14: What is the MOQ once the spec sheet is approved?

A: 500 pcs per style per colour. Confirm the colourway split before the deposit, because fabric is booked per colour and a change after booking adds time to a bulk calendar that already runs 35-50 days from approved sample and deposit, FOB Xiamen.

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