The SportHunter 1825 can be easily expanded to control up to 6 dogs by adding Sport DOG Brand Add-A-Dog collars. User can select from 8 stimulation levels each within low, medium or high setting on the compact receiver. Vibration and tone options further help you build a customized remote training system to guarantee the best performance from your dog. The SD-1825 system is also fully customizable, allowing you the flexibility to set 2 or more transmitters to control the same Collar Receiver. With a 1 mile range, a slim-profile Collar Receiver that ensures a perfect fit, and a compact remote transmitter that’s easy to handle, the SD-1825 delivers on our promise: Gear the way you’d design it.