Tri-Tronics collars are one of the highest quality electronic dog collars on the market today. The Pro 500 G2 EXP is the top-of-the-line model thats favored by top professional trainers. It includes18 levels of momentary and 6 levels of continuous stimulation. Other features include: True one-hand operation, No-slip grip on transmitter On/off collar switch Rugged antenna Long and short contact points provided No-stimulation signal tone Train up to three dogs from the same transmitter (purchase extra receivers separately). You are able to add receivers later with the ability to field marry new receivers to your transmitter easily - extra straps (red & blue) for future dogs included with transmitter. 2-year manufacture warranty