Bundle of 2 items - SportDog - SD-425 - SDR-AF Two Dog Field Trainer for Introductory and Advanced Training Dog Waterproof Shock Collar This is a bundle of 2 items: SportDog SD-425, SDR-AF SD-425 Field Trainer with SDR-AF is two dog system recommended for dogs 8 pounds or larger with low to moderate temperament. This waterproof collar has 7 levels of stimulation plus vibration and tone that can be switched instantly. It features up to 500 yard range and is expandable up to 3 dogs without losing any functionality with additional collar.. SD-425 system has rapid 2 hour rechargeable battery, which is designed to last for up to 50-70 hours depending on frequency of use