E-Collar K9-402 2 Dog Handler 3/4 Mile Remote TrainerThe K9 402 K9 Handler is the 2 dog version of the K9 400. It is a 3 4 mile range trainer loaded with unique features making it the most humane and effective trainer available with the smallest rechargeable dog training collar receiver in the world. But, dont be fooled by the small receiver size 2X1. 5X1 2. 4 ounce, it provides plenty of stimulation for most dogs. The unique COS (control of stimulation) technology provides very clean stimulation