Farewell to bulky, large and heavy clothing. Stay warm, sleek and stylish under your favourite fashion in chilly weather. Warm up your upper back to increase core temperature. Soothe stiff back and fuse your discomfort in a soft, handy and sustainable way. The yarn used in a HarnessWarmer is recycled from two PET bottles. control / smartphone app: five heat-setting levels & maintain constant temperature 15/30/60-minute timer *smartphone app can connect up to 6 KnitWarm products at the same time