UV400 Lenses, Base Curves, MOQs and Test Reports: The Specs Wholesale Sunglasses Buyers Actually Need to Verify

UV400 Lenses, Base Curves, MOQs and Test Reports: The Specs Sunglasses Buyers Actually Need to Verify

 

Written by Cedric | Production & Technology Mamber at Leeyewear, a sunglasses manufacturer with over a decade in eyewear production

Last updated: September 8, 2026

Here's something we see almost every week. A buyer lands on our site, loves a frame, and the first question is: "Can you make the lenses darker?" Darker. Not safer. Not more protective. Darker.

 

If you're sourcing custom sunglasses from a manufacturer for the first time, that question tells us a lot. Lens darkness is the single most misunderstood spec in this industry. So let's go through what actually matters when you place a bulk order: UV protection standards, base curves, lens thickness systems, MOQs, filter categories, and those test reports everyone keeps asking for at the wrong moment.

A dark lens can be more dangerous than no lens at all

This isn't a scare tactic. It's optics.

A dark lens blocks visible light, the part your eyes notice. UV protection is a separate function that depends on absorbers built into the lens material. The two have nothing to do with each other. Now here's the part most buyers miss: when you wear a dark lens with no real UV filtering, your pupils open up, which lets more unfiltered ultraviolet straight into the eye. Eye care authorities have warned about exactly this. A cheap dark lens can be worse than nothing.

And it's not just an optics problem. It's a legal one. The WHO links UV exposure to cataracts, pterygium and photokeratitis, and attributes roughly 10% of the world's 15 million cataract-related blindness cases to UV exposure. If a batch sold as "UV protection" doesn't actually protect, the liability chain runs straight back through the importer and the brand. That's why we'd rather lose an order than ship lenses we can't back up with data.

UV400 vs UV380: the 20-nanometer gap that separates pros from pretenders

Quick numbers, because this is where specs get lazy:

UVA radiation extends all the way to 400 nm, so a UV380 lens leaves exactly that slice unprotected. The American Academy of Ophthalmology puts it plainly: look for UV400 or "100% UV protection". They mean the same thing, blocking 99–100% of UVA and UVB.

One industry habit worth knowing: printing "UV400" on a lens costs a supplier almost nothing. Running an actual spectral transmittance test does not. Guess which one the cheap factories skip.

Swapping lenses isn't "just a swap": base curve, thickness and lens shape

Buyers ask us all the time: "This frame is in stock. Can you fit it with a different lens color or function?" Usually yes. But three things have to line up first.

1. Base curve. Every frame is designed around a specific lens curve, from Base 4 (almost flat, classic optical styles) up to Base 8 (deep wrap; most sport frames need an 8-base, and the lens curve should match the frame within about 0.5 diopters to assemble cleanly). The curve belongs to the frame, not the lens. Force a Base 4 lens into a Base 6 frame and you get a loose fit, stress marks, lenses that pop out. Do the opposite and you're bending the lens against the groove until it cracks. So step one of any lens swap is simple: confirm the frame model with us and we'll check its curve.

2. Thickness, and here's where it splits into two worlds.

Thick-lens systems (CR39, PC, nylon): these are cut or injection-molded as solid pieces. PC sunglass lenses typically run 1.6–2.2 mm center thickness, CR39 usually 2.0–2.2 mm. On these, a steeper curve and bigger diameter genuinely push the edge thicker. That's basic sag geometry. There is no universal published table for it, because front curve, back curve and tolerances all shift the numbers. Our advice: make your supplier quote both center thickness and edge thickness in writing. A single number is marketing; two numbers are engineering.

Thin-film systems (TAC polarized): a completely different animal. A TAC polarized lens is a laminated film, with polarizing PVA film sandwiched between TAC layers plus UV absorbers and a hard coat. Industry-standard thickness comes in three tiers: 0.75 mm, 1.0–1.1 mm, and 1.4–1.5 mm. The factory presses the whole sheet to your frame's curve, commonly anything from 2C to 8C. So with TAC, thickness is really three questions:

• Curve stability: pressing a thin 0.75 mm sheet into a deep 8-base wrap risks optical distortion. For high-curve sport frames, we steer buyers toward 1.0 mm minimum.
• Impact resistance: the polarization is identical between 0.75 and 1.1 mm. The difference is purely toughness and durability. Daily fashion styles: 0.75 mm is fine. Kids' and sport styles: go thicker.
• Rimless reality check (from our own production floor): a thin TAC sheet can't hold a nylon-cord groove, so semi-rimless designs are off the table, and drilled rimless needs a thickness assessment first. If your line includes those constructions, tell us before sampling, not after.

3. Lens shape and blank size.

Custom-tinted or gradient lenses get cut to the frame's shape, and the blank has to clear it with margin: minimum blank size = effective diameter + (2 × decentration) + 2 mm. Same curve, different shape. Different cost, different feasibility.

Lens swaps are frame-matched, not lens-picked. Send us the frame model plus the lens effect you want (color, polarized or not, gradient or solid) and we confirm compatibility before quoting. This one step has saved our buyers more money than any spec sheet.

Choosing your lens system: six materials and five filter categories

Six lens materials, mapped to product lines

Our take after years of quoting OEM sunglasses programs: the smartest brands build product tiers on a single frame mold. Same frame, an AC base version and a TAC polarized version, with a 2–3× retail price gap between them. That's a typical outcome in our programs. Don't spec every style to the max. Put money where your customer actually feels it: impact resistance and polarization for sport lines, mirror flash for fashion lines. Margins get healthier, not thinner.

Five filter categories, and why "category" is not "UV protection"

Under EN ISO 12312-1, sunglass lenses are classified by visible light transmittance (VLT), from Category 0 to 4:

Two things buyers consistently get wrong here:

Category is not UV protection: They measure completely different things. A Category 0 clear lens can be genuine UV400; a Category 4 near-black lens can block zero UV. 

Mirror coatings quietly change the category: In real production, a mirror coating trims VLT by roughly 15–25%. Take a Category 3 blank at 10% VLT, flash a standard mirror coat on it, and the finished lens can dip below 8%. At that point you own a Category 4 product with driving-ban labeling obligations. The category of a coated lens must be measured after coating, on the finished lens, not copied from the blank's spec sheet. We suggest writing that into your purchase spec.

One real-world recipe

Say you're building a "resort casual" line for a US boutique chain. Our default suggestion: TAC polarized UV400 (function), Category 3 dark gray tint (the volume category), blue Revo flash on the front (the look), 1.1 mm to keep unit cost at volume-tier levels. That combo clears CE in the EU, clears the FDA drop-ball requirement in the US, and meets the AAO's UV400 guidance.

Lens functions and coatings: every extra has a bill attached

Beyond UV, here's what can be stacked onto a lens:

Two field tips from our QC bench. First, every added function means one more coating pass at the lens plant, so cost and lead time climb together. Don't stack functions on a $5 promo style. Second, the cheapest supplier test we know: drag a key lightly across the lens back where nobody looks. An uncoated bare lens shows scratches immediately. It takes ten seconds and tells you more than a spec sheet.

What Is the MOQ for Custom Sunglasses? for stock lenses and 500 for custom

"We only need 100 pairs. Can you do it?" Sometimes! But let us show you the plumbing behind the number.

Stock lenses (MOQ 300 pairs): these are the high-volume SKUs lens plants keep on the shelf year-round, and honestly, it's almost always the same one: dark gray polarized UV400 TAC. It sells everywhere, so plants stock it deep. Anything beyond that, gradients, mirror colors, special tints, has thin or zero stock coverage. If you want an off-catalog color, send us a physical lens sample or clear photos of your target color. Photos and Pantone color samples set the color direction; they cannot lock the exact shade. On polarized lenses, the polarizing film itself is a gray base layer, which shifts how every dye reads. The same green tint looks noticeably different on polarized versus non-polarized lenses.

We source across the whole supply chain against that target. If it exists, 300 pairs works. If it doesn't, we're into custom.

Custom lenses (MOQ 500 pairs): any personalized tint, gradient or coating means the lens plant opens a dedicated dye bath or coating run. Their internal minimums typically sit in the thousands of pieces. By the time that filters down to us assemblers, 500 pairs is the realistic floor we can negotiate. The threshold isn't ours. It's upstream.

Once you see this mechanic, the hardest combination in sourcing becomes obvious: small volume plus heavy customization. Which brings us to the next topic.

Test reports: what they're actually for, and when you'll get them

A test report is not a negotiating token you collect at inquiry stage. It's a compliance tool that earns its keep at three specific moments:

• US customs clearance:  Every lens sold in US eyewear must pass the FDA's impact-resistance rule, 21 CFR 801.410, the drop-ball test: a 5/8-inch steel ball dropped from 50 inches onto the lens, which must not fracture. Each shipment needs a compliance certificate to accompany it.
• Market compliance: The EU requires conformity to EN ISO 12312-1:2022+A11:2024 with CE assessment. US retail buyers commonly gate on ANSI Z80.3.
• Your downstream audits: Brand owners, chains and marketplaces will want these files on record from you.

In normal trade, we provide all of this with the shipment, once the order reaches production stage. What we genuinely can't do is hand over full report packs at the inquiry stage, for two boring, practical reasons. One: on a 50-pair job, no upstream lens plant will produce a report at all. Two, and we'll say this carefully: the industry has a habit of suppliers' reports circulating into price-shopping exercises that never convert into orders, and those documents carry our registration data. That's not hostility. That's self-preservation.

And here's the part we wish more buyers understood: sourcing is a two-person dance, not a one-sided favor. A real case from this quarter. A European buyer wanted 80 pairs of premium acetate sunglasses, beautifully specced, full brand customization down to meticulous packaging details, and three different gradient lens colors on one single frame. We searched our own warehouse, then the entire supply chain. No matching gradient lenses existed anywhere we could reach. The buyer wouldn't flex on a single detail. That project is still frozen. Not because anyone refused to cooperate, but because customization crossed past what the supply chain can physically deliver. When that happens, the only way forward is both sides moving one step: agree on what's possible first, then chase what's perfect.

If you're serious about a project, here's the path that actually works: share your product idea and rough quantity, we respond with lens feasibility (stock, sourcable, or custom-only), then sampling, then reports and documentation. Every step is backed by something real, and the reports end up doing their actual job.

Three more details that quietly sink orders

1. Nickel release: Under EU rules (REACH), nickel release is restricted on metal parts in prolonged skin contact: frames, hinges, and metal nose pads. If you're shipping metal styles to Europe, ask for the material report before you ask for the price.
2. "FDA certified" is a tell: The FDA registers facilities; it doesn't certify companies. A supplier advertising "FDA approved" or "FDA certified" either doesn't understand the system or hopes you don't. The real moves: facility registration, device listing, batch-by-batch drop-ball records.
3. Trace the certificate to the actual lens maker: A drop-ball certificate passed along by a pure assembler (a frame factory that buys lenses in) frequently fails customs audit scrutiny. Worth one extra question at quoting: who issued this, and who actually made the lenses?

What Leeyewear can do for you

We run an OEM and ODM eyewear factory in China, and we work the way this article describes. Concretely:

Lens programs: stock polarized UV400 TAC lenses from 300 pairs; custom tint, gradient and mirror from 500 pairs. Off-catalog colors? Send your physical sample or photos and we search the full supply chain.

Frame-lens matching: we verify base curve, thickness and shape compatibility before quoting, and run assembly-validation samples where needed. This applies to our sunglasses lines and to our custom optical frames / acetate optical frames as well, if you're building a mixed collection.

Compliance documents: drop-ball certificates per 21 CFR 801.410, CE technical documentation, plus SGS,ISO 9001.

OEM/ODM frames: acetate, TR90 and metal constructions; logo work in laser engraving, silk print or metal badges. For wholesale sunglasses programs and private label sunglasses lines alike, the same engineering discipline applies.

Packaging: two routes. Your logo printed on our stock neutral packaging (boxes, pouches, cloths) from 300 sets; or fully custom structures, where die-cutting and printing plates are one-off mold costs. Realistically 500 sets minimum, comfortably 1,000 if you want the per-unit price to make sense. Tell us the packaging concept and we'll cost it straight.

Sampling & lead time: stock-style samples ship within 10 working days. Fully custom projects depend on which parts need tooling: lenses, molds, packaging. Send us your project by email and we'll confirm a real timeline, not a hopeful one.

Tell us your target market and product concept. We'll tell you straight what's possible and what's not. →

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FAQ

Q1: I only need 100 pairs. Is that workable?

Depends, in a good way. If you pick our stock dark-gray polarized UV400 lenses and a stock frame that matches them in curve and shape, 100 pairs is very likely doable. The moment either side needs custom work, the relevant MOQ takes over. Send us the target model and we'll check real stock and give you a straight answer.

Q2: What's the process for fitting gradient lenses to an existing frame?

Send the frame model (or a physical sample), we confirm base curve, thickness and shape, you send your target gradient reference, we source or quote custom, then assembly-validation sample, then mass production. The feasibility check isn't optional. It's the step that prevents a full-batch rework.

Q3: When do I get the test reports?

With the shipment, once your order is confirmed for production. For small-quantity jobs in the dozens of pairs, upstream report generation needs a separate conversation. We'll tell you the real timeline and cost.

Sources:

WHO - Ultraviolet radiation and health

American Academy of Ophthalmology (aao.org) - Sunglasses: How to Choose the Best Lenses

US FDA - 21 CFR 801.410 Impact Resistance of Lenses; 21 CFR 886.5850

EN ISO 12312-1:2022+A11:2024 - Eye and face protection: Sunglasses

ANSI Z80.3 - Nonprescription Sunglasses

TAC lens thickness & curve specs - supplier spec sheets, HKTDC fair listings, Lansee Optic spec-sheet guide

Filter category VLT ranges - ISO 12312-1:2013 category table (BioMedical Engineering Online, PMC8086354); College of Optometrists tint guidance; Swiss FOPH sunglasses factsheet

Mirror coating VLT impact - Karuson OEM buyer guide (industry field reference)