The SF series provides maximum heating performance in a small 12-volt DC furnace. The SF model is offered in five sizes from 20,000 to 40,000 BTU/h input. Only 7-1/2" H, it can be easily installed in low height areas. Eleven duct connection choices, top, front, side, and bottom, top or side rear gas and electrical connections make it easy to install. An optional exterior access door allows for furnace service without entering the coach. Unit Size: 7 1/2" H x 17" W x 20" D. Thermostat sold separately.