Fourth Elements answer to the electrically heated vest or undergarment. Utilizing the body's own heat output and retaining it, weight for weight the X-Core is Fourth Elements warmest undergarment yet. Pair it with an Arctic, Halo 3D or Arctic Expedition (see SKU's: PCKDA1, FRTXT500T, FRTH3TP) to experience warmth without batteries or wires. The sleeveless design of the vest minimizes 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, minimizing cold points. The additional chest panel helps to minimize the rush of cold air from the inlet valve of dry suit 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. Designed to be worn under an Arctic, Arctic Expedition, Halo 3D or any other dry suit undergarment, X-Core augments thermal protection to the extent that electric heating can be avoided in many instances. It performs best over a lightweight base layer such as J2 or Xerotherm (see SKU: FRTX