Best Folding Sunglasses in the UK: A Buyer's Guide

Folding sunglasses solve one problem: the good pair you left at home. A pair that folds down to pocket size is a pair you actually have with you when the sun comes out. But folding adds moving parts, and moving parts are where cheap sunglasses fail. This guide covers what to check before you buy, and how the main options on sale in the UK compare.

1. The hinges matter more than anything else

A folding pair has more joints than a normal pair: usually one at the bridge and one at each arm. Every one of them takes stress every time you fold and unfold. Look for metal hinges held with screws you can tighten, rather than plastic pins. Sprung arm hinges are a bonus: they flex outward so the arms grip without squeezing, and they take knocks without bending out of shape.

On Folds, the arm hinges are sprung and open to 120 degrees, and a mini screwdriver comes in the box so you can keep them tight.

2. Frame material: TR90 or acetate?

Most quality folding frames are either acetate or TR90. Acetate is the traditional choice and polishes up beautifully, but it is heavier and can crack if it is sat on. TR90 is a flexible thermoplastic that bends under pressure and springs back, which suits something that lives in a pocket. It is also lighter and hypoallergenic. We go into more detail in TR90 vs Acetate.

3. Lenses: polarised and UV400 as a minimum

Two separate things to check. UV400 means the lens blocks ultraviolet light up to 400 nanometres, which covers UVA and UVB. That is the part that protects your eyes. Polarised means the lens filters horizontally reflected light, which is what causes glare off water, wet roads and car windscreens. That is the part that makes them comfortable. Cheap folding sunglasses often have one but not the other, so check both are stated clearly.

4. Check the lens category

Every sunglass lens has a filter category from 0 to 4, based on how much visible light it lets through. Category 2 lets through 18 to 43% and suits everyday UK sun. Category 3 lets through 8 to 18% and suits very bright conditions. Category 4 is too dark to drive in. For most people in the UK, Category 2 or 3 is the right choice. Our guide to Category 2 vs Category 3 explains which suits you.

5. How small does it actually fold?

Some "folding" sunglasses only fold at the arms, like any normal pair. True folding frames also fold at the bridge, halving the width. Check the folded size and the case: a slim case that fits a pocket matters more than a hard case you will leave behind.

6. Fit

Folding frames vary in size, so check the lens width (the first number in measurements like 51-20-140) against a pair you already own. Sprung hinges give extra room for wider heads.

7. Warranty

Because folding sunglasses have more moving parts, the warranty tells you how confident the maker is in its hinges. Two years is good; three is better.

The main options in the UK

• Folds (£49.95). Flexible TR90 frame with metal-core arms, polarised UV400 Category 2 lenses, sprung hinges, 19 g, vegan leather case, 3 year warranty. Sent from the UK. One frame shape in black or tortoiseshell.
• Ray-Ban Folding Wayfarer (RB4105). The famous name, with the classic Wayfarer shape. Typically well over £100 at UK retailers, and the standard version is not polarised. See Folds vs Ray-Ban RB4105.
• Foldies. A US brand with several frame styles, polarised Category 3 lenses and a two-year warranty, sold mainly in US dollars from its US website. See Folds vs Foldies.
• Budget folding sunglasses. Plenty on marketplaces for under £20. Some are fine as a spare; many skip polarisation, use plastic hinge pins and come without a warranty.

The short version

Look for metal hinges, a flexible frame, polarised UV400 lenses in Category 2 or 3, a slim case and a warranty of at least two years. That is the brief we built Folds to.