The Surestim 2 dog units have a pager feature in the handheld transmitter acknowledging that you have fully engaged the transmitter button. This positive feedback vibration feature is especially valuable when wearing gloves during cold weather training and hunting. Designed for dogs over 20 lbs. The colar/receiver and transmitter is fully waterproof. Features LCD screen which displays exact level of stimulation even in dark or low light conditions. Three bar battery life indicator.