Aetertek AT-211sw Replaced Receiver or Transmitter Aetertek 211D receiver replacement. Can be used as 1 dog, 2 dog training system (extra collars needed for 2 dog training) Very small but effective, especially suit for small dog even cat Water-resistant (not waterproof ,can not be immerse in water) dog collar receiver Environmentally friendly---Rechargeable remote and receiver, save $$$ on buying replaceable batteries .(Note :Since the receiver is very small,its battery need to be charged after every one and a half days' training . ) Beep tone function + vibration correction + 10 Levels of progressive shocks