The SportDOG Field Trainer 400S provides all of the benefits of the Field Trainer 400, with the addition of higher stimulation levels for larger or stubborn dogs. It is loaded with technical breakthroughs in the smallest package available in this price range. Features such as 3-dog expandability and waterproof/submersible transmitters and receivers are among the most advanced benefits ever offered in a mid-range remote training device. With 400 yards of range, these palm-of-the-hand size models are designed for field training and hunting. Choose either tone or stimulation to train your dog. A low-battery detection feature monitors your transmitter and receiver. Rechargeable Ni-MH batteries, a lanyard, and a limited lifetime warranty are included.