The Fourth Element Xerotherm is the ultimate base layer for use under a dry suit. Made using Polartec Power-Stretch which was originally developed for NASA, the Xerotherm traps a layer of air - a much better insulator than water - next to the skin, keeping the wearer drier and more comfortable. The range is designed to be worn under another under suit or on its own under a neoprene dry suit and provides astonishing warmth without contributing to bulk or buoyancy. In fact, the buoyancy effects of the Xerotherm are so small that they rarely impact on weight configuration, yet dramatically improve warmth.

The Xerotherm represents the ultimate in base layer performance, unrivalled by anything else on the market. Xerotherm has been to the top of Everest and down to the Titanic, as well as being specified by the FBI Dive Teams, Norwegian Navy and British Police Diving Units. Xerotherm provide excellent thermal protection and comfort. Constructed using flat locked stitching and single layer high wicking fleece fabric; it protects the legs and complements the Xerotherm under suit range with high waistband design to prevent separation of the top and leggings during the dive. It is low bulk and can be worn under other thermal bottoms without making dry suit too tight or uncomfortable. The knit of the Xerotherm fabric produces the fastest wicking effect of any of the products in the fourth element product range. Moisture is drawn out through the fabric along fine fibers and then spreads out over the outer surface. This maintains a thin layer of air (a more efficient insulator than water) next to the skin. This is so effective in the Xerotherm that some wearers report experiencing minor suit leaks during the dive without even noticing until after the dive. As a standalone undergarment, the Xerotherm is suitable for thermal protection in water temperatures of 66.2Degree F to 68Degree F (19Degree C to 20Degree C). Stirrups on the legs make donning a dry suit on top of the Xerotherm easy. The leggings are black in color and are available in multiple sizes. Updated for 2018 with new men's and women's fits. Fabric is 53% polyester, 38% nylon and 9% elastane.