PETARMOR Flea & Tick Collar effectively kills fleas and ticks on your dog. This two-pack of PETARMOR Flea & Tick Collars provides protection against fleas and ticks for up to 1 year (Use one collar per dog at a time). This one size-fits-all flea and tick collar is intended for dogs 12 weeks and older. Each durable, water resistant collar can last up to 6 months. It doesn't lose effectiveness against fleas and ticks even if it gets wet. Simply slide the collar on your dog, lock into place, cut off excess length, and you're good to go.