Tri tronics 2 dog collar system. This is the flyway special. The batteries in the collars need to be replaced and it works great. If you buy this, replace the batteries, and it doesn't work, I'll refund your $200. I'm certain it will work. As a matter of fact, I think one of the collars works alright now. I haven't used it in a few years but I guarantee it will work. Call or text 785-259-3202