This is the 4th Element Men's X-Core Vest Drysuit Undergarment Features: Exceptional warmth Contains 76% recycled polyester Four-way stretch fabric for snug fit Sleeveless design - complete freedom of movement for valve shut downs Additional thermal layer on chest panel Perfect next-to-skin or over a baselayer Fast wicking fabric keeps wearer drier and warmer Heavyweight Polartec Power Stretch Blue Sign and Oeko-Tex certified Odour resistant Machine washable 76% recycled polyester / 16% polyester / 8% elastane Designed to be worn under an Arctic, Arctic Expedition, Halo 3D or any other drysuit undergarment, X-Core augments thermal protection to the extent that electric heating can be avoided in many instances. It performs best over a lightweight baselayer such as J2 or Xerotherm but the X-Core can also be worn as a next-to-skin garment for critical core protection. The Fourth Element X-Core Womens Sleeveless Vest Top, The sleeveless design of the vest minimises impact on buoyancy and overall bulk especially in the shoulders and arms where freedom of movement is critical. The four-way stretch fabric combined with long body design ensures a snug fit, minimising cold points. The additional chest panel helps to minimise the rush of cold air from the inlet valve and provides extra thermal protection in a key exposure area. The fast wicking fabric moves perspiration towards the outer surface, keeping the wearer drier and warmer.The physiological response to cold stress is to reduce blood flow to the periphery and look after the body core, where it can often just be a matter of time before cold becomes the limiting factor in the safety and enjoyment of a dive. X-Core provides extreme thermal protection to the core, enabling longer, more comfortable dives.