The Castelli Pro Issue SS Base Layer is a superlight, super-comfortable baselayer that performs brilliantly and has topped my list of go-to layering.
Castelli says in the blurb that the garment was created after requests from the pro peloton; those guys know what they want and it translates well into a piece of clothing the rest of us will appreciate.
Made from 100% polyester 3D mesh fabric, first impressions are that it doesn't seem to weigh anything, and if you are a bit prudish it is almost see-though. Lingerie it is not, though, and its credentials include a wider neck for a better fit under a tight collared or aero jersey, reduced seaming on the shoulders for comfort, and a flat hem so it doesn't create a point of irritation on the waist.
Personally I wear a baselayer by default whatever the weather, partly for comfort but mostly for the moisture wicking they provide, so this top got a lot of use. It's really nice to wear, easy to get on and off dry or wet, despite being race cut and therefore snug, and being so light and comfortable when on to the point that you don't notice it's there at all after a while.
As with most Italian brands, you need to pay attention to the sizing. They are nearly always notoriously small; I take a medium usually but this XL was just about right, and an XXL might have been perfect. At no point does it feel tight or pinch, though. The material is very stretchy and forms to the body well, the minimal seams and flat hem making it almost like a second skin.
Castelli recommends a 10-20°C range for the garment, which basically covers the UK summer – in the early summer climate at home I wore it in rotation with some of my standard polyester construction baselayers for comparison and it shone far above all of them. I did wonder if the 3D mesh might make it a little too cool as it looks too thin to be of any benefit in warmth terms, but it did just as well as the solid construction layers I have.
For moisture-wicking, my main reason for wearing a baselayer, it massively outdid the others – this is where that 3D mesh really works, pulling the sweat away from the skin. I recently covered a two-week trip from the UK to Portugal via Spain, through the interior of the country where we experienced temperatures peaking at 37°C, and even though well out of its recommended range it performed admirably, not adding to the heat retained but keeping me cooler by wicking away the moisture well, despite being wet through.
Considering the use it has had, it still looks great now, with no rips or pulls in the thin fabric and the printed Castelli logos staying complete despite numerous washes, both in the machine and by hand while travelling. Another bonus is that its construction leaves it almost dry after the spin cycle or hand-wringing, getting it back into service in double-quick time.
At £35 it's pretty good value too, considering the high performance on offer. It sits in between cheaper short sleeve polyester baselayers from the likes of dhb and BTwin, and more expensive merino items which aren't always too useful in the summer months.
Overall, a top quality product that the professionals are happy to wear and you should be too.
A superlight and high performance baselayer that works in many different conditions – no wonder the pros use them
road.cc test report
Make and model: Castelli Pro Issue SS Base Layer
Size tested: XL
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?
The SS baselayer is a super-light garment designed to operate best in temperatures in the 10-20°C range, wicking moisture away from the body quickly.
Castelli says: "The Castelli Pro Issue SS - base layers aren't only about keeping warm, the main reason for wearing a base layer is to wick moisture away from the skin and the Castelli Pro Issue SS base layer does this better than any."
Tell us some more about the technical aspects of the product?
The garment is made from 100% polyester 3D mesh fabric, with reduced seaming at the shoulders for extra comfort, the collar is wider for better aesthetics under an aero jersey and the flat waist hem sits better under shorts. It's light too at 48g for the L size.
The stitching is tight and neat, with no loose ends or obvious flaws.
I wore the baselayer numerous times in the UK within (and under) the recommended temperature range and also in 30+ degree heat in Spain and Portugal. The baselayer worked as expected, wicking sweat away quickly leaving me comfortable on the bike, even in those hot temperatures. My preference is to wear a baselayer at all times and although saturated, it never felt uncomfortable.
There have been no issues at all with the garment up to this point, but its light and very thin construction do leave it vulnerable to rips or tears should you snag it on something or you have a washing machine with a tendency to damage delicate clothing.
The material is very stretchy, so the race fit will adjust to your body shape and comfortably so, never feeling restrictive or tight anywhere.
The garment is a typical Italian (read small) sized fit, so you'll need to size up over a standard UK fit. The XL tested here was just about right, an XXL would have been perfect – I usually wear a medium UK size.
It really is featherlight at 48g for the XL, and barely more for the bigger sizes.
To the touch it is soft, and after a few minutes you don't realise it's on – the lack of seams and lower neck line translate into a very comfortable piece of kit. Even when in operation and wet with sweat there is no rubbing or feeling of being damp.
For the high performance on offer the price sits well, in between the cheaper short sleeve polyester baselayers from the likes of dhb and BTwin and the more expensive merino items which aren't always too useful in the summer months.
How easy is the product to care for? How did it respond to being washed?
I washed it multiple times in the machine on a cool wash without issue, and while away on a two-week road trip it was hand-washed almost every day with a drop of sports wash and was almost dry when wrung out – it then took minutes to actually dry when hung up, which was most useful.
Tell us how the product performed overall when used for its designed purpose
The baselayer performed perfectly on every ride, wicking moisture away and adding a little extra warmth when needed. In the heat on the Continent the extra layer didn't make me any hotter, but the transfer of sweat from the skin was good even though it was way above the intended temperature range of the garment.
Tell us what you particularly liked about the product
The low weight, comfort and performance were all notable highlights.
Tell us what you particularly disliked about the product
Sizing is a bit of a gamble, being Italian; it can be difficult to know how many sizes to go up from standard UK sizes.
Did you enjoy using the product? Yes
Would you consider buying the product? Yes
Would you recommend the product to a friend? Yes
Use this box to explain your score
Exceptional? Well, it's one of the best and most comfortable lightweight baselayers I have ever used, doing exactly as advertised. It's so easy to wash and dry you could use it daily if needed – a big plus if you ride lots or commute.
About the tester
I usually ride: Boardman AirPro Di2 My best bike is:
I've been riding for: 10-20 years I ride: A few times a week I would class myself as: Expert
I regularly do the following types of riding: road racing, time trialling, cyclo-cross, commuting, club rides, sportives