Bontrager B1 Sleeveless base layer review

At first sight, the Bontrager B1 Sleeveless base layer looks like a very lightweight option. But it’s not quite as light as it looks, with the fabric used a bit denser than some of the competition. The Profila Cool fabric has a mesh structure, with areas of thinner fabric between the more structural parts.

>>> Buy now: Bontrager B1 Sleeveless base layer from Trek's webstore for £32.99 (opens in new tab)

There’s also not as much stretch as in other summer base layers we’ve tested, so it’s more important to make sure that you’ve chosen the correct size for you. Fortunately, there are six size options available, from X-Small to XX-Large, so you should be able to find a good fit.

The less stretchy fabric means that the Bontrager B1 Sleeveless base layer fits closely, so it wicks sweat away effectively and keeps you very comfortable as you ride. There’s good length and a dropped tail, so it tucks nicely under a jersey and into your summer shorts. The grey seams are slightly raised. They are not uncomfortable though and at least some seem to be aimed at supporting the Bontrager B1 Sleeveless base layer’s structure rather than actually connecting together multiple fabric panels.

>>> Buy now: Bontrager B1 Sleeveless base layer from Trek's webstore for £32.99 (opens in new tab)

Like the Mavic Hot Ride base layer, which we’ve also reviewed, there’s a mix of fabrics which includes 37.5 tech. This is claimed to absorb and release heat, helping to keep your body working at its optimal 37.5 degrees centigrade. That makes up around 19% of the fabric content, with the balance being 66% polyester and 15% spandex.

Also like the Mavic Hot Ride, the Bontrager B1 Sleeveless base layer comes in white only. It suffers from the same tendency to stain yellow from sunscreen as a result. It’s one of a range of eight summer base layer offerings from Bontrager, which includes both sleeved and sleeveless numbers, with separate cuts for men and for women.