UV numbers look like trivia until a customer, a customs officer or a regulator asks you to prove what your sunglasses actually block. Here is what the numbers mean and why the difference matters commercially.
The numbers themselves
UV400 means the lens blocks wavelengths up to 400 nanometres — the full UVA and UVB range that reaches the eye. UV380 stops at 380 nm, leaving a small sliver of UVA unblocked. For markets where sunglasses are treated as a protective product (the EU and the US in particular), UV400 is the expectation.
Why it is a commercial issue, not just a technical one
- Labelling and claims: you cannot advertise UV400 protection on sunglasses that only reach UV380.
- Regulatory: the EU treats sunglasses as personal protective equipment in many cases; UV400 test reports are commonly requested at import.
- Returns: a lens that fails a buyer’s UV tester becomes a return, a refund and a lost customer.
What to ask for
Ask for test reports — not just a statement on a spec sheet. A credible supplier can supply a UV400 test report for the lens used in the shipment you received.
Darkness is not protection
A dark tint without UV filtration is worse than no sunglasses at all: it opens the pupil wider while letting UV through. Tint level (category 1–4) and UV filtration are separate properties, and both should be documented.
Our stock sunglasses ship with UV400 lenses and the reports that go with them — our certifications page explains what comes with each order. Questions on a specific style? Ask us.