What Is Yulex? Plant-Based Rubber, Explained
What Yulex is, how it compares to neoprene and whether it is as warm. A plain answer from the first triathlon brand to use it.
Date:
September 28, 2026
Time:
4 min
Somebody in your swim group has a Yulex suit and they have probably mentioned it. Possibly more than once.
Behind the slight evangelism there is a genuinely interesting material, and a question most people have not had answered properly: what is it, and does it actually work as well as the stuff it replaces?
The Short Answer
Yulex is natural rubber, tapped from the Hevea tree, refined into a closed-cell foam. It does the same job as neoprene in a swimming suit. It keeps you warm, it does not soak up water, and it stretches.
The difference is where it comes from. Neoprene is made from petrochemicals. Yulex grows.
Why that matters more than it sounds
Rubber is one of the few genuinely renewable industrial materials. A Hevea tree is tapped rather than felled, it keeps producing for decades, and the plantation keeps standing.
Zone3 states that plant-based rubber cuts a garment's CO2 emissions by up to 80% against neoprene. That is a large number and worth reading carefully: it is a comparison of the rubber, not of an entire garment's life, and we would rather give you the figure with that caveat attached than let it sit there looking bigger than it is.
The linings are recycled polyester, which is the less glamorous half of the story and matters roughly as much.
Is it as Warm
Yes, at the same thickness. This is the question everybody asks and the answer is unexciting.
A closed-cell foam traps warmth by holding tiny pockets of gas in a structure that water cannot get into. Yulex does that in the same way neoprene does, so a 1.5mm Yulex layer behaves like a 1.5mm neoprene one. What changes your warmth is thickness, coverage and fit, not whether the rubber came from a tree or a refinery.
Where you might notice a difference is in feel. Natural rubber has a slightly different stretch, a little softer and less snappy. Most people stop noticing within a swim or two.
What we make with Yulex
Three suits, all 1.5mm, and all designed around the same idea: a layer you can wear on its own or underneath something else.
The Sleeveless Swimsuit is the one most people start with, because it warms your core without doing anything to your shoulders.
The Long Sleeve Swimsuit adds arm coverage with a front zip, a seamless underarm panel and zig-zag cuffs that stop water flushing through.
The Kneeskin covers core and thighs and leaves the arms completely free, which is why it suits paddleboarding and surfing as well as swimming.
All three work over swimwear while the water is still mild, and as a base layer under a wetsuit once it is not. That second use is the one people tend to discover in November and wish they had known about in September.
The honest limits
A 1.5mm layer is not a wetsuit. It extends your season and it will not take you through February on its own, and anyone who tells you otherwise is selling something.
We also do not publish a natural-rubber percentage, because we would rather not quote a number we cannot stand behind. If a brand gives you a precise figure, it is worth asking what it refers to.
And no temperature rating, from us or anyone reputable. How cold you feel depends on how long you are in, how acclimatised you are, and what the wind is doing to the back of your neck.
FAQs
What is Yulex made of?
Natural rubber tapped from the Hevea tree, refined into a closed-cell foam. The linings in our Yulex suits are recycled polyester.
Is Yulex as warm as neoprene?
At the same thickness, yes. Both are closed-cell foams and both trap warmth the same way. Thickness, coverage and fit matter far more than which rubber is used.
Is Yulex better for the environment?
The rubber is renewable and Zone3 states that plant-based rubber cuts a garment's CO2 emissions by up to 80% against neoprene. That figure compares the rubber rather than the whole garment lifecycle.
Can you wear Yulex under a wetsuit?
Yes, and it is one of the better reasons to own a piece. The same suit works over swimwear in mild water and as a base layer underneath once it gets colder.
How thick is Yulex swimwear?
Our Yulex suits are 1.5mm. That is a season-extending layer rather than a replacement for a wetsuit.
Does Yulex last as long as neoprene?
Cared for the same way, yes. Rinse it in fresh water after every swim, dry it out of direct sunlight, and store it on a wide hanger rather than folded.
Worth knowing
We were the first triathlon brand to use Yulex, which means we have had a few years of people asking whether it really works. It does. The more useful question is whether a 1.5mm layer is what you need right now, and that depends entirely on how cold your water is and how long you want to stay in it.
