Custom Dial-A-Temp™ rheostat manually controls the temperature of your dog heat mat. Operates at 120 volts. Calibrated to 23V (+ / – 3V) at lowest setting. Maximum current ratings at 3 Amps RMS. Output capacity of 300 watts. UL listed. Enclosure measures 3 x 2.25 x 2.5 in. Keep your pets warm with a pet heating pad.