I got this singlet along with Gore's windblocker cool weather singlet to wear as a base layer for cool spring riding in Seattle. I'm really impressed with the quality of both, but unfortunately couldn't wear this singlet due the the size of the arm opening. I'm usually a Medium or Large, so I got the Large, since Gore generally runs small. The fit is snug, but not too tight, but the arm openings are so small they pinch me in the under arm and I'm sure will cause chafing with extended use.
The Windstopper singlet strangely (but fortunately) has a different shape arm opening which is much more comfortable.