See photos and description - Celliant material is unique for UA, and still very stretchy! These have only been worn once. What is CELLIANT? CELLIANT bioceramic infrared technology. CELLIANT works by absorbing and converting body heat from the wearer into full spectrum infrared energy. This is clinically demonstrated to temporarily increase local circulation and, improve cellular oxygenation and improve, boosting strength, stamina and endurance and supporting temperature regulation. The infrared advantage provided by CELLIANT wearable technology helps Under Armour, through the UA RUSH™ collection, fulfill its promise of optimizing human performance. What is HeatGear®? Under Armour HeatGear® technology is UA’s solution to keeping cool while training in warm conditions. The fabric is designed to be very lightweight, and to wick sweat away from the skin and diffuse it through the material so it can evaporate more quickly. The fabric is also highly breathable, perfect for hot days.