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b'Twin Aerofit Wind Undershirt



Comfortable, well-fitting, base layer at its best in sub-zero conditions

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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The b'Twin LS Aerofit Wind base layer from Decathlon is part of the French sports superstore chain's extensive array of cycling kit which covers everything from socks through to full bikes. The brand is growing year on year and on the whole value for money is the main drive.

At £34.99 the LS Aerofit Wind is positioned near the top of a range of baselayers that starts at just £5.99. The 'Wind' part of the name comes from the polypropylene front panel intended to keep your core warm against cold winds. The membrane runs from the chest down to the abs, exactly where you're going to take the breeze when in a crouched road position.

The rest of it is made up of a 97% Nylon/3% Lycra mix knitted at varying weights to create mesh style sections for breathability. The widest mesh is under the arm pits for the greatest heat transfer while the back panel carries a tighter mesh section down the centre and either side, ideal for rucksack/hydration pack users.

Around the waist the Aerofit Wind is contoured inwards to create a close fit which is what you want as a baselayer becomes more effective the closer to the skin that it is. The material doesn't quite offer a level of compression for a full second skin fit which as it's called Aerofit I'm guessing it is intended to have.

The hem, neck and cuffs are knitted, creating grip without the use of silicone or elastic grippers, which I find much more comfortable; it stayed in place no matter how much I changed position.

The mild winter we're having so far highlights the Aerofit Wind's intended temperature is around the freezing mark if you wear it under a softshell or windproof jacket. It can get pretty warm as your effort increases. If you're an early season racer needing to display your club/team colours though, it's perfect under a standard jersey up to around 10 degrees.

When riding on the odd cold day, -5°C I think was the lowest, the Aerofit Wind finds its sweetspot especially when you add in the windchill factor. Your chest and lungs benefit the most from the extra insulation. Breathability isn't quite as good as some merino options but if it does get wet from perspiration you do at least stay warm.

On the whole the Aerofit Wind offers a good fit with its dropped tail and the performance is impressive as long as you give your layering options some consideration before you set off. The material is soft against the skin with no itching or irritation from the seams which themselves look well constructed.

Black is the only option although colour choice isn't a major worry for most when it comes to baselayers and there is a wide range of sizes from S-XXL. With b'Twin backing all of this up with a two-year guarantee makes value for money look pretty impressive against other similar products on the market.


Comfortable, well-fitting, base layer at its best in sub-zero conditions.

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Make and model: Btwin Aerofit Wind Undershirt

Size tested: Medium

Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

It's a baselayer designed for cold, especially windy conditions thanks to the membrane front panel. It is very warm though and is best used in conditions below freezing.

Tell us some more about the technical aspects of the product?

It uses a membrane front panel to act as a windbreak while the rest of the material uses varying levels of mesh for breathability.

Rate the product for quality of construction:
Rate the product for performance:
Rate the product for durability:
Rate the product for comfort, if applicable:
Rate the product for value:

Tell us how the product performed overall when used for its designed purpose

Its on the warm side and being synthetic means it doesn't breathe as well as merino. The fit is good though as is the comfort.

Tell us what you particularly liked about the product

The fit and cold temperature performance.

Tell us what you particularly disliked about the product

You might not get much use out of it this winter unless we get a decent cold snap.

Did you enjoy using the product? Yes.

Would you consider buying the product? Yes.

Would you recommend the product to a friend? Yes.

Overall rating: 7/10

About the tester

Age: 35  Height: 180cm  Weight: 76kg

I usually ride: Ribble Winter Trainer for commuting, Genesis Flyer  My best bike is: Sarto Rovigo

I've been riding for: 10-20 years  I ride: Every day  I would class myself as: Expert

I regularly do the following types of riding: time trialling, commuting, club rides, sportives, fixed/singlespeed,


With 20 years of road cycling and over 150,000 miles in his legs it's safe to say Stu is happiest when on the bike whatever the weather. Since writing his first review for back in 2009 he has also had a career in engineering including 3D-CAD design and product development, so has a real passion for all of the latest technology coming through in the industry but is also a sucker for a classic steel frame, skinny tyres, rim brakes and a damn good paintjob.
His fascination with gravel bikes is getting out of control too!

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