The Thermo X is 13oz of pure performance and comfort. With its water repellency and odour resistance properties this top will keep your core toastie. The 4 way stretch fabric, rash protection, strategic seamless paddle zones and low crew neck ( no interference with wetsuit neck ) means the only thing you need to concentrate on is nailing that one manoeuvre!!! ( also great as an under garment for any sports where you need another layer, running, mtb, etc )