Castelli summer skullcapin hot weather sweat in the eyes can sting making for an uncomfortable ride this summer skull cap fits under your helmet and wicks away perspiration also featuring a mesh top panel for ventilation featuresmaterial 81 polyester 19 elastanewicking layer to keep sweat out of your eyesmesh top panel for ventilationfits under helmetbuy castelli clothing from chain reaction cycles the worlds largest online bike store