Castelli Core Seamless Sleeveless Base Layer Review 2026
What It Is A base layer earns its place under a tri suit or jersey by doing one job well — wicking sweat away without adding bulk or chafing. The Castelli Core Seamless Sleeveless is built from a knit of 84% polyester and 16% polypropylene, and the seamless construction is the headline feature: no stitched…










