Board Shorts & Swim Shorts OEM: Fabric, Lining, Chlorine, MOQ

Board shorts and swim shorts are the two beach cuts designed to go into water on purpose, and that single fact rewrites the specification. A beach short worn over a swim brief needs a fabric decision. A board short or a swim short needs a lining system, a chlorine-fastness result, hardware that does not corrode, and seams that hold when the garment is pulled on wet. Those are the four items an OEM beach shorts supplier in China is quoting against, whether or not the enquiry names them.

This article covers the swim side of the programme: how lining is specified and attached, how ISO 105-E03 is run and what number passes, where the garment fails under load, and what a buyer should demand before approving a swim line. The cut-by-cut comparison sits in beach shorts versus board shorts versus swim trunks, and the substrate decision sits in the quick-dry fabric guide.

What does a swim programme need that a beach short does not?

Four requirements appear on a swim tech pack and usually do not appear on a beach short one.

• Sustained water contact. A beach short is splashed; a swim short is submerged, sat in, and pulled on while wet. Every seam and attachment point sees repeated load in a soaked state, which is a different mechanical test from dry wear.
• Chlorine. Pool water carries free chlorine, and chlorine is an oxidising agent. It attacks dye molecules and it attacks elastane. A colour that passes a wash test can still fail a chlorinated-water test, and a waistband can lose recovery long before the shell shows wear.
• A lining system. Either the garment has a liner or the buyer supplies one separately. There is no neutral answer: the choice changes the pattern, the seam list, the drying behaviour and the price.
• Hardware in a corrosive environment. Eyelets, drawcord tips, zips and any metal trim sit in salt water and chlorine. Plated zinc alloy that is fine on a street short will bloom white within a season.

Everything else — print method, waistband style, inseam, leg opening — is shared with the beach short programme and is covered in the comparison article.

Which lining system belongs in the tech pack?

Five lining options cover almost every swim and board short programme in the market. The table is the one worth pasting into a specification review, because the attachment column is where quotations go wrong.

Two rules decide whether a liner survives. First, state the attachment points: waist and both side seams, not waist only. A liner joined at the waist alone has nothing to resist the pull at a leg exit, and it tears at the side seam within a few wears — a defect that only appears once the garment is wet and in use. Second, state the liner fabric and weight: a 70 gsm polyester mesh and a 170 gsm polyester-elastane jersey are not interchangeable, and quoting one against the other is a price error that surfaces at the sample stage.

For board shorts, unlined is the norm in the surf trade, because the garment is worn over a separate swim brief. For swim shorts sold into retail, a liner is expected in most markets, and its absence becomes a returns issue rather than a saving.

How is chlorine fastness tested, and what number actually passes?

ISO 105-E03 is the method: colour fastness to chlorinated water, written for swimming-pool water. The edition that appears on most buyer test lists is ISO 105-E03:2010, edition 4, and it sets three alternative test conditions. In the standard’s stated test conditions, active chlorine at 50 mg/l and 100 mg/l is intended for swimwear, while 20 mg/l is intended for accessories such as beach robes and towels. The specimen is treated in the chlorine solution, rinsed, dried, and assessed for change in colour against the grey scale in ISO 105-A02.

The concentration is the part buyers misread. A maintained pool runs at roughly 1–3 mg/l free chlorine (industry practice; it moves with bather load and local code), so a 50 mg/l test is an accelerated exposure rather than a simulation of one swim. That is deliberate — it compresses a season of pool use into a laboratory cycle. A shell that has only been tested at 20 mg/l has not been tested for swimwear at all.

Grading runs from 1 to 5 in half steps. The threshold is set by the buyer, not by the standard; a retail programme typically asks for 4 or better on colour change (industry practice). Two failure patterns are worth naming in the defect list: prints on polyester that shift shade rather than lose depth, and dark navy and black grounds that go patchy where the garment folds in water.

Three practical points decide whether the result means anything:

• Test the assembled garment, not the greige shell. A shell that passes over a white lining can fail once the lining is dyed and the two bleed into each other.
• Run ISO 105-E03 alongside ISO 105-C06 (washing), ISO 105-E04 (perspiration) and ISO 105-B02 (light). They fail for different reasons; a programme that tests one is guessing about the other three.
• Ask for the report, not the mill’s scope certificate. The report names the laboratory, the condition (50 or 100 mg/l), the grade and the date.

Chlorine also attacks elastane, which is a failure separate from colour. A waistband can lose a measurable share of its recovery over a season and still pass every colour test, and the buyer only finds out from returns. If the programme is a pool product, specify chlorine-resistant elastic or a covered elastic with a polyester wrap, and ask the mill which chemistry the elastic uses — chlorine-resistant grades are a distinct product, not a finish applied afterwards.

Where do board shorts and swim shorts fail under load?

Four points take almost all the failures: the crotch seam, the fly corner, the waistband join, and the leg opening of the liner.

Crotch seam. On a board short the crotch carries the load of a wet garment being pulled up and of a leg being lifted. A single-needle lockstitch there fails at the seam before the fabric goes. Specify flatlock or four-needle six-thread (ISO 4915 type 607) at the crotch and inner leg, and bar-tack the seam ends.

Fly corner. On a hook-and-loop or short-zip fly, the corner is where the pull concentrates. The fix is a bar-tack plus a reinforced facing, not a longer stitch run; a longer stitch simply moves the failure point down the seam.

Waistband join. Where the elastic is joined, the seam sees the full stretch of the waist every time the garment goes on. A three-step zigzag or a butt seam with a covering stitch holds; a plain overlock does not.

Liner leg opening. The liner is the part that rubs, and its attachment at the side seam is where it separates. Double-stitch the attachment and check it by hand at inspection, not by eye — a partly detached liner looks intact on a table.

Seam strength can be measured rather than argued about. ISO 13935-2 gives the grab method for maximum force to seam rupture, and a buyer can put a minimum figure on the purchase order. The number is programme-specific, but the test ends the argument about whether a seam is strong enough.

Gusset. A bonded or double-layer gusset at the crotch is standard on surf-oriented board shorts. It changes the pattern and adds a pressing step, and it removes the seam that would otherwise sit against skin in a wet garment. State whether the gusset is sewn or bonded: the two are not interchangeable on a cost sheet, and they carry different care instructions.

Which hardware survives chlorine and salt water?

Metal trim on a swim garment has two jobs — not to corrode, and not to release nickel onto skin. Both are testable, and both belong in the specification rather than in the inspection remarks.

• Corrosion. ASTM B117 neutral salt spray is the usual method for eyelets, zips, rivets and drawcord tips. A 24-hour exposure with no white corrosion product is a common buyer threshold (industry practice). Plated zinc alloy usually fails it; stainless steel or a powder-coated part usually passes.
• Nickel release. Under REACH Annex XVII, items in prolonged skin contact must not release more than 0.5 µg/cm²/week, measured to EN 1811 with the wear and corrosion preconditioning of EN 12472. A drawcord tip or an eyelet that touches skin falls inside that scope.
• Plastic alternatives. Where the design allows, moulded plastic eyelets and aglets remove both problems and are lighter. They also remove the metal finish some programmes want, which is a design decision to take at tech-pack stage, not at inspection.

Chlorine is the harder environment for metal than salt water. A part that survives a seaside holiday can still pit in a heated indoor pool over a season, so treat the salt-spray result as a floor rather than a guarantee.

Where do print, labels and packing enter the swim programme?

Print is a fabric decision with a fastness consequence. Sublimation dyes polyester fibre and wraps a seam without a white line, which is why all-over print swim shorts are almost always sublimated; it does not work on cotton, and it does not work on a coated nylon shell. Whatever the method, the print carries the same ISO 105-E03 requirement as the ground shade — a print that passes wash and fails chlorine looks correct in the showroom and faded after two pool sessions.

Labels and packing are where a custom beach shorts supplier in China earns or loses the order: the programme needs your own print artwork, your woven main label, your care label with the correct ISO 3758 symbols, and your polybag and carton markings — all four fixed before the sample is cut, because each one adds a file, a position and an inspection point.

The care label deserves its own line. The wash condition printed on the label must not be harsher than the condition the shell was tested to under ISO 105-C06, or the garment is being instructed to fail. ISO 3758 supplies the symbol set; the wash temperature, the bleach instruction and the drying method are the buyer’s decision, and they should match the test report that sits behind them.

Two compliance items attach to the shell rather than to the construction. A recycled polyester shell can only be labelled recycled where the mill holds GRS or RCS and can issue a transaction certificate for the lot — a scope certificate names the mill, not the fabric in your order. And for a US programme, 16 CFR 1610 flammability is a mandatory standard rather than a buyer option: the buyer holds the test report, and the compliance obligation sits with the US importer.

How do you test whether the best beach shorts supplier in China can run a swim programme?

The question is phrased that way because the label is a claim, and a claim needs evidence. Eight checks separate a supplier who can run a swim line from one who can run a beach short line and is quoting anyway.

1. A named mill and lot per colour. Not a fabric name — a mill, an article number and a lot, so a repeat order lands on the same substrate.
2. A chlorine report on the assembled garment. ISO 105-E03 at 50 or 100 mg/l, graded, dated, from a laboratory the buyer can call.
3. A written lining specification. Liner fabric, weight, and the attachment points, on the tech pack rather than in an email.
4. Seam strength data. ISO 13935-2 results on the crotch and side seams, with the stitch type stated.
5. Hardware documentation. Nickel release to EN 1811 and a salt-spray result to ASTM B117 for every metal part.
6. An inspection plan. AQL to ISO 2859-1, with the defect list written for prints, elastic and side seams rather than copied from a woven shirt.
7. Sampling dates in writing. A development sample in 12–18 days and a PPS in 5–7 days are commitments, not estimates.
8. Label and packing files closed before sampling. Artwork, woven label, care label and polybag specification all approved at PPS stage at the latest.

Each of the eight is a document rather than an opinion. A supplier who can produce six of the eight is probably workable; one who can produce two is selling a beach short with a liner added, and the chlorine test is the first thing that will show it.

How does the OEM run work, from tech pack to FOB Xiamen?

The sequence is fixed, and the dates only hold if the specification is frozen before sampling starts.

• Specification review. The tech pack is checked for the four swim items — lining, chlorine test condition, hardware, seam type — before a price is issued. A quotation that arrives before this review is a guess with a number attached.
• Development sample, 12–18 days. Cut in the nominated shell and liner, with the print method the fibre can take.
• PPS, 5–7 days. Pre-production sample in the bulk fabric and bulk trims, with labels and packing as they will ship.
• Bulk, 45–60 days for a first order and 30–40 days on a repeat, because the fabric and the print setup already exist.
• Inspection to AQL under ISO 2859-1, on the defect list agreed at PPS stage.
• Shipment FOB Xiamen, 30% on order confirmation and 70% against a copy of the B/L.

Minimum order for this line is 3,000 pcs per style per colour, which is set by the liner minimum, the print setup and the cutting table time for a colourway — not by a policy figure. Quotations are issued FOB Xiamen and stay valid for 30 days.

Where Unitex fits

We are Xiamen Unitex Trade Co., Ltd., a sourcing and trading company working with partner manufacturers in China — in the trade since 2009, incorporated in Xiamen in 2013, with partner factories holding amfori BSCI and OEKO-TEX® STANDARD 100. We are not the factory and we do not present ourselves as one; the value we add is the specification review, the test list and the inspection plan that sit between the buyer and the line.

Board shorts and swim shorts run through the same custom beach shorts programme as the rest of the beach line, alongside the men’s underwear OEM programme that shares the same partner network and the same audit structure. If you are weighing a swim line against a beach short line, send the reference sample and the destination market: the answer usually comes down to which test list the market requires and whether a liner is expected in that channel, not to which garment looks better on a hanger.

What should the buyer send first?

Six items are enough to get a specification review rather than a price:

• A reference sample or a photograph of the cut, with the intended water contact.
• The lining decision, or the line that says the garment is unlined.
• The shell and liner fabric, or the fabric you want nominated.
• The destination market, because it decides the test list and the labelling rules.
• The print artwork, or the number of colourways if the print is still open.
• The quantity per style and per colour, so the minimum can be confirmed before sampling.

With those six, a swim programme can be quoted against a test list instead of against a photograph. Without them, the quotation is for a garment that does not exist yet, and the difference only shows up at inspection.

Last updated: 2026-10-29 · Xiamen Unitex Trade Co., Ltd. — OEM & ODM underwear sourcing partner

Unitex Underwear (Xiamen Unitex Trade Co., Ltd.) — OEM/ODM underwear sourcing and supply-chain partner in Xiamen, China; in the trade since 2009, incorporated in 2013. Based in the Xiamen–Quanzhou–Jinjiang knitwear cluster, Fujian Province, south-east China.