Dt systems h2o 1810 plus series training collar with "add-on" capability offers the maxx-range internal antenna system, the industrys only internally woven antenna in the collar. With up to a one mile range, they are perfect for hunting, basic obedience, and professional training. H2o plus series collars feature sixteen levels of intensity easily selected by one hand for maximum control and safety. Each model includes both momentary "nick" and continuous stimulations. The transmitter and collars are both 100-percent waterproof. The transmitter floats on water and the collar can be worn even when the dog is submerged. The h2o plus series dog training collar is durable, safe, and very humane when used correctly. The automatic safety shut-off feature stops the stimulation after 8 seconds to prevent accidental or prolonged stimulation. D.t. Systems helps bring out the best in your best friend.