Rechargeable, Waterproof Receiver Collar - Quickly charges in 2-3 hours with each charge lasting up to 2 months depending on use. Adjustable Receiver Collar - With 4 levels of static correction and tone, fits pets 5 lb or more with neck sizes 6 to 26 inches. Add Unlimited Pets - With the purchase of compatible PetSafe In-Ground Fence receiver collars (Excludes YardMax® and UltraSmart®). Surge Protector - Helps protect your transmitter from lightning strikes and powers surges.