Thinskins is O'Neill's performance series designed to protect against wind chill, UV exposure and wax irritation in warm to tropical conditions. The 0.5MM neoprene insulation throughout provides core warmth and rib protection while the super-stretchy material allows for freedom of movement for swimming, surfing, paddling, and more. Features:100% Ultraflex DS offers superior stretchStrategic seamless paddle zonesPerfect to pair with boardshorts or a pair of neoprene shorts; can also be used to layer underneath a wetsuit for more versatility Boardshort connector loop and cinch system on lower hem Maximum UV protectionReverses to solid black Choose your size from the chart on the Size Tab. Note: These shirts are designed to fit very snugly in order to insulate well. If in between sizes, choose the larger size, or order both & return the one that does not fit.