Used once. The ZONE3 neoprene swim cap (size L) is a highly insulating item suitable for swimming in cold water temperatures. It primarily uses 4mm thick Yamamoto smoothskin neoprene to provide excellent head insulation. Features: • Insulation: Heat-tech lining and smoothskin material retain heat, effective for long swims in open water. • Fit: The under-chin Velcro strap prevents slippage, and size L is for head circumferences of approximately 57-59cm. • Usable year-round.