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Castelli Seamless Sleeveless base layer



High performance base layer that is a man-made alternative to merino in the anti-stink stakes.

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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It might look like a string vest but Castelli's seamless sleeveless base layer is a top quality cycling undergarment that shifts sweat off your skin and doesn't get smelly despite daily use.

Comfort and good wicking properties are the two fundamental requirements when it comes to a good base layer.

Castelli gives the seamless sleeveless base layer great wicking properties by using two different materials, a polypropylene layer next to the skin and a nylon outer layer. Both have very little absorbency making them ideal for transferring perspiration and humid air away from the body through the mesh pattern of the base layer. The nylon provides some elasticity and as long as it isn't stretched too far it will retain its shape over a long period of time.

Castelli has varied the mesh pattern throughout the base layer so that it has bigger gaps in the material where you're likely to get warmer. The underarms, chest and upper back are the main parts to receive this treatment.

Both nylon and polypropylene can be melted which allows seams to be created without stitching and how the garment gets its seamless moniker. The joins run around the edges of the mesh panels adding strength to the base layer.

Versatile & comfortable

The Seamless Sleeveless is part of Castelli's Spring/Summer range and although its nominal temperature range is 20°C to 35°C it works very well in much cooler climes. Down to around 12°C has been fine in short sleeve jerseys and under a winter jersey it's been fine at low single figures.

Comfort is very good, the thicker material (compared to the likes of Craft's Cool Mesh that I normally wear) makes it feel a little bit odd as you pull it on but once in place it contours to the body and feels great. It's a good length and doesn't ride up when you're in the drops. The high close fitting neck stops any unwanted drafts.

Regardless of effort the wicking properties are some of the best I've known and whether you've finished an interval session or a 100 miler the Castelli is virtually dry having passed the perspiration out to your jersey to evaporate.

Low whiff

Surprisingly for a man-made garment the whiff-o-meter hardly registers a reading after a week's riding (2 hours a day commute) and when it has been bunged in the wash its come up clean every time and no signs of shrinkage.

Overall it's a top performer in the world of base layers and a price of £35 is hardly extortionate for the quality and performance you're getting. It comes in a sleeved version to and three sizes of small, medium and large. As per usual with Castelli kit its best to err on the larger size from the norm.


High performance base layer that is a man-made alternative to merino in the anti-stink stakes.

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Make and model: Castelli Seamless Sleeveless base layer

Size tested: n/a

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?

Castelli describe the Seamless Sleeveless as one to wear on every ride. Designed specifically for warmer temperatures I found it'll happily work on its own down to single figures.

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

Varying mesh sizes for specific heat transfer and the use of nylon and polypropylene means seams can be welded for brilliant comfort.

Rate the product for quality of construction:

Very well put together.

Rate the product for performance:

Works a treat in all conditions.

Rate the product for durability:

Loads of washes and plenty of time stuffed screwed up in a kit bag hasn't bothered one bit. Still looks as new.

Rate the product for weight, if applicable:

Nylon and polypropylene are two of the lightest materials on the market.

Rate the product for comfort, if applicable:

Very soft against the skin.

Rate the product for value:

Under forty quid is pretty impressive for a top-performing base layer.

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


Tell us what you particularly liked about the product

The comfort and performance.

Tell us what you particularly disliked about the product

You need to keep it covered up as a string vest isn't the greatest of looks.

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: 9/10

About the tester

Age: 34  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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