SportDOG Field Trainer for Stubborn Dogs, SD-400S Radio-controlled pet training system with transmitter and collar Adjusts for higher-intensity electric stimulation for larger, more stubborn dogs 400-yard range for hunting, farm and field work; expands to 3 dogs with purchase of additional collars Instantly change stimulation intensity from the transmitter; tone only button Lightweight collar measures 1-1/2 by 2-1/2 by 1-1/4 inches (width by length by depth)