Add a second collar to your existing PetSafe Remote Trainer with the Add-A-Dog Receiver Collar. This collar is waterproof up to 5 feet and rechargeable with the wall adapter (included). The adjustable strap fits neck sizes up to 28". It is compatible with the following Regular versions of PetSafe Remote Trainers - 300 Yard Remote Trainers PDT00-16024 & PDT00-16117, 600 Yard Remote Trainers PDT00-16027 & PDT00-16120 and 900 Yard Remote Trainer PDT00-16123.