This is the Bare 3mm Vest Thermal Layer with S-Flex For Scuba Diving Features: Pullover style layering piece for added warmth under any full suit Edges finished with stretch nylon binding Double glued with SECURE-LOCK construction Material: 3mm S-FLEX neoprene with FULL-STRETCH and THERMALSKIN in Innovation: S-FLEX is developed from a proprietary blend of neoprene that generates extreme levels of stretch for an easy in, easy out of the suit, improves comfort and mobility, and is wrapped in a buttery soft exterior finish When a diver needs a little more thermal protection than their full suit can provide, this soft, comfortable S-FLEX layer ensures a soft, supple fit and increased warmth on colder dives.