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. Both units are 7 1/2" in diameter. They are 1 1/4" high and come with a 6" cord and two-prong plug. Good for just about any drinker, from a gallon to 2.5 gallons. The Bullet style heater fits the European Drinkers. The molded projection is about 3" in diameter and 1 1/4" high. Supplied with a bulb. The maximum temperature that the Heavy Duty Heaters will reach is between 75 degrees and 86 degrees.