Bundle of 2 items - SportDog - SD-425S - SDR-AS - Two Dog Field Trainer for Large or Stubborn Dog Waterproof Shock Training Collar This is a bundle of 2 items: SportDog SD-425S, SDR-AS SD-425S and SRR-AS two dog system is designed for stubborn dogs that require higher levels of static stimulation. Rapid 2 hour rechargeable battery, which is designed to last for up to 50-70 hours depending on frequency of use. Recommended for dogs 8 pounds or larger. This waterproof collar has 7 levels of stimulation plus vibration and tone modes. It features up to 500 yard range and is expandable up to 3 dogs with additional collar without losing any functionality.