Alpha 100 helps you track and train up to 20 dogs from up to 9 miles away touch screen display plus 18 levels of momentary and continuous stimulation. Compatible with the following collars: TT25 T20 TT15x T5x TT15 TT15 mini T5 T5 mini TT10 This particular unit is in like-new condition. It's clean, field-ready, has very little visible wear, and a 30-day warranty! Includes wall charger.