SportDOG SD-1825 Transmitter Compact Remote Transmitter Up to 16 levels of stimulation (low, medium or high setting) Compatible with: SD-425, SD-425S, SD-425CAMO, SD-825, SD-1825, SD-1825CAMO, SD-1875 Contents: Remote Transmitter, Antenna, Belt Clip and Lanyard Expandable up to 6 dogs