Heater features stranded resistance copper/nickel alloy wire heating element for longest life, not cheaper etched aluminum foil like other heaters. Solid State temperature control maintains waterbed temperature within 1/10 of a degree. Cheaper b&c heater controls can vary temperature by 3 degrees, a difference you can feel. Overlimit switch prevents overheating. For use with Hardside/Wood Frame Type Waterbeds. Made in USA.