Easy to use adjustment lever allows temperature to be precisely set in 0.5° increments.Push lever to left for 5 seconds to change from Cº to Fº. Push lever to the right or left for 1 second to change the set temperature up or down. (Each push of the lever will change the set temperature by 0.5º)Set temperature range is between 68ºF and 93ºF. 10" long and rated for tanks up to 15 gallons.