SportDog - SD-425 - Field Trainer for Introductory and Advanced Training Dog Waterproof Shock Collar SD-425 Field Trainer is 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 expendable up to 3 dogs without losing any functionality. 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.