Ursuit Thermofill Heavy undersuit

Ursuit Thermofill Heavy undersuit is designed specifically as a warming layer to be worn under a drysuit. The Thermofill Heavy undersuit is made of a technical multi-layer material that makes the suit breathable, elastic and water-repellent. The outer layer is X-Tex membrane fabric, the insulating layer is Thermofill fibre and the inner layer is pleasant fleece. The structure of the Thermofill insulation is unique: its binding element is a weft in the middle of the fibres, to which the insulating fibres are attached. This makes it an extremely flexible, airy and particularly durable insulation. The difference from traditional nonwoven wadding is decisive: Thermofill does not clump, flatten or break down even after years of use, and it withstands countless washes without losing its insulating ability. Laminating the Thermofill insulation to a breathable and waterproof membrane fabric and a fleece lining creates a combination that takes undergarments into a new era. The Heavy model is designed for extremely cold conditions.

The insulation of the fabric used in the Thermofill suit has been measured with the international Clo value: 0.83 for the Light model and 1.97 for the Heavy model. Features include ventilation holes in the armpits and, for diving use, in the left arm, a two-way front zip, a zippered chest pocket, generous thigh pockets, fleece cuffs at the collar, wrists and ankles, and a sturdy waistband. The structure of the wrist and ankle cuffs makes dressing easier by preventing the sleeves and legs from riding up while putting the suit on.

Product text updated 9.10.2026.