The castelli prosecco long sleeve baselayer is made for cool conditions or even high intensity cold weather rides where wicking moisture away from your skin in the first goal the hydrophilic prosecco treatment spreads the moisture out over a larger area for quicker evaporation they use 2 different weights of fabric with the thinner layer used where it will be covered by your shortstights or bib straps so that your dont have too much insulation where you dont need it