This product is an extra collar for the DT Systems H20 1810 and 1820 PLUS. It can be paired with the handheld, which can pair up to three collars per system. If you are looking for a training collar that is great around the house as well as in the field, look no further than DT Systems H2O 1810 PLUS. This 1-mile range collar system has 16 levels of momentary (or Nick) and Continuous Stimulation. Both the collar unit and the transmitter are completely waterproof. In fact, the transmitter will actually float on water; perfect for all you waterfowlers who spend more time on the water than the ducks do.