The heating element is insulated on the bottom and radiates heat to the top surface. Uses 110-120 AC. Features beveled edges and an extra support rod. Comes in single or double size. Can be installed with or without thermostat-based temperature controls. When installed without temperature controls, mat will heat to a constant temperature of 37?F above ambient temperature.?36 Single size features 64.17 watts; 48 single size features 84.33 watts, 36 double size features 128.33 watts, 48 double size features 168.66 watts. 36 size has 18 stainless steel electrical cord protector with a 10' electrical cord.?48 size has 20 (1-1/2 dia) PVC cord protector, 10' cord, comes with 45? elbow and 2 mounting brackets.?48 sizes require a UPS special handling charge.