Aquarium Heater for Fresh or Salt Water Temperature Control Dial Automatic safety shut-off switch 2mm shock resistant glass - outperforms the 1 m thickness of other heaters Completely waterproof Approved to UL 1018 6 foot double insulated power cord Clip on heater holder Control light Window Precision bi-stable thermostat with plus or minus 1/2 degree F holding temperature. Free of radio and TV interference. Specs: 50 watt - 9" Heater Length 75 watt - 10" Heater Length 100 watt - 12" Heater Length 150 watt - 13" Heater Length 200 watt - 15" Heater Length 250 watt - 17" Heater Length .