This base layer has a thicker mesh than some others I have so it lets more air flow between the jersey and skin. It's more like a chain link fence than continuous fabric. It's very lightweight. I'm sure it's designed to fit tight, but consider sizing up. I thought I was buying a size too big and it's a struggle to get it off. On the road though it feels fine.
Firstly, thanks to all the previous reviewers this item runs very small. I took the advice of others and bought 2XL and it fits perfectly, a little long but will tuck in nicely. I'm 5ft 10in, 37-38 chest 165 lbs. Usually medium rapha jersey, large castelli jersey and large pro castelli base layer. But this base layer just about fits like the large pro issue castelli which is for me a size up already. Other than sizing I can tell merely by the design that this base layer is what you want for a hot day above 85 degrees F. I wear the normal and sleeveless castelli pro base layer in 80- 85 degree weather but above that I feel hot. The pro castellibbase layer is thinner than the core 3 but the pro does not have actual openings between the mesh just varied thickness and is very thin. This is the next level with large mesh openings. Hope this helps.
My only problem is sizing. I am 5'9" and weigh 160 lbs. and I normally consider myself a medium body. I know Castelli tends to the small side so I purchased a l/xl baselayer. It is still too small. However, it does keep me cooler on hot, humid days.
fits very tight and very uncomfortable was not a good buy for me
The core mesh creates an isolating layer that promotes warmth in the cold and allows heatmoisture to escape when the morning ride heats up. It fits snuggly like all Castelli products. Only drawback is the tag placement on the side, needs to be removed.
I'm a female and use this base layer. Comfortable and keeps me cool. If I tug it up just a tad I don't feel the bottom seam on my bare skin. I always order up and fits perfect and snug. Mesh makes this base layer breathable. I'm able to open up my jersey comfortably.
Other versions of this kind of mesh are stretchy and wear out quickly. This one is less stretchy, but seems to be higher quality that will prevent it from getting disgusting and completely disintegrating.
It's for hot days to stay cool, but also works great under another base layer for cold days to trap heat against your body.