The castelli free 9 sock our rosso corsa sock was the basis for the free 9 sock but we39ve added a new mesh construction to the cuff to make it a bit cooler for summer the graphics look great with any castelli product but they were specifically designed to match the new free jersey and free bibshort castelli free 9 sock features perfect for hot conditions meryl skinlifereg antibacterial yarns diaphanous mesh on foot and ankle reinforced cuff keeps sock in pl