Strobel Organic Waterbed Heater Solid State for Hardsides Copper/nickel alloy wire heating element for longest life Solid State temperature control maintains waterbed temperature within 1/10 of a degree Over limit safety switch prevents overheating For Hard side Waterbeds Made in USA by Strobel Copper/nickel alloy wire heating element for longest life Solid State temperature control maintains waterbed temperature within 1/10 of a degree Overlimit safety switch prevents overheating For Hardside Waterbeds Made in USA by Strobel