SportDOG Brand TEK Series 2.0 GPS Tracking + E-Collar Add-A-Dog Collar - Additional, Replacement, or Extra Tracking + Training Collar - Waterproof and Rechargeable with Tone, Vibration, and 99 Levels of Shock - TEK-2AD-C

The tek-2ad-c add-a-dog location and training collar lets you add another dog to your existing TEK series 2.0 System. In terms of range, accuracy, and reliability, the TEK series 2.0 Tracking and training system surpasses every other system on the market. This system can track up to 21 collar receivers/handhelds so you can cover your whole pack.