Round Lab's US sunscreen: why a Korean favourite came back reformulated, and what "UV Lock" means for you

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Researched. We have not used this one long enough to give you a verdict, and we would rather say so than invent one. What follows is how it works, who it suits, and what it will not do. When we have used it properly, this page carries the verdict and the date.

Round Lab Birch Juice UV Lock Sunscreen

Round Lab's Birch Juice Moisturizing Sunscreen built a following as one of the most comfortable sunscreens in Korean skincare. It is one of the names climbing fastest in searches right now. If you buy it in the US, though, you will get a version with a different name — "UV Lock" — and the reason is worth understanding.

Why the US version is different

In the US, sunscreen is an over-the-counter drug, and only a short list of UV filters is approved for it. Many Korean sunscreens rely on newer filters that are not on that list, so they cannot be sold here as they are. According to the listing, this UV Lock version was developed to keep the soothing, moisturizing character of the original while meeting US rules for SPF 45 broad spectrum, and it is OTC registered.

That is the version to want. A Korean sunscreen bought from an unofficial seller may be the original formula, untested and unlabelled to US standards. This one is sold by Round Lab's own store.

What SPF 45 broad spectrum covers

SPF 45 is a measure of protection against UVB, the burning rays; broad spectrum means it has also passed the US test for UVA protection, which matters for long-term skin damage. We explain the difference in what SPF measures, and what it leaves out.

The texture

The listing describes a lightweight, non-greasy essence texture with no white cast and a natural finish that works under makeup. It also highlights that NBC Select's editors ranked it first among more than 100 sunscreens they tested — a review by others, not a promise from us.

How to use it

As the last step of your morning routine, after serum and moisturizer, according to the listing, patted onto face and neck. Use enough — around a quarter of a teaspoon for face and neck — and reapply every two hours outdoors. The listing says it is gentle enough to use near the eyes and washes off with an ordinary cleanser.

Who it suits

Dry and normal skin that wants a comfortable, moisturizing sunscreen, and sensitive or breakout-prone skin — the listing says it has been tested for low irritation. It comes as a two-pack, which is sensible for something you should be using up quickly.

What it will not do

It will not protect properly if you use too little or never reapply. It will not be the same formula as the one sold in Korea. And it will not replace shade and a hat on a long day in strong sun.

The product

The US-registered, SPF 45 broad spectrum version of a much-loved Korean sunscreen, sold as a two-pack by Round Lab's official store when we checked. For a lighter, serum-like option, see SKIN1004's sun serum.

The one people are searching for is the ROUND LAB Birch Juice Moisturizing UV Lock SPF 45, 2-Pack.

Round Lab Birch Juice UV Lock Sunscreen

We do not print prices here, because a price we typed last month is a price that is wrong today.

Written by JamieG in Garner Town, Tennessee.