A heavy duty plastic round heater that is great in cold climates. It is a continuous heater that stays on all the time, regardless of the outside temperature. Each unit has a small red light that goes on when it is plugged in and in this way, if for some reason your unit is not working or the power is off, you know at a glance. 7 1/2 in. in diameter. They are 1 1/4 in. high and come with a 6 in. cord and two prong plug. Good for just about any drinker, from a gallon to 2.5 gallons. Should you like to control the heat, we would suggest a Thermo Cube-Cold Weather double plug. The #2188 goes on when the temperature drops to 20 degrees and shuts off when the temperature goes to 30 degrees and above. The Bullet style heater fits our European Drinkers #3527, #3528, and #3529. The molded projection is about 3 in. in diameter and 1 1/4 in. high. The maximum temperature that the Heavy Duty Heaters will reach is between 75 degrees and 86 degrees.