The Seresto Cat Vet-Recommended Flea & Tick Treatment & Prevention Collar for Cats is fast-acting and long-lasting to protect your furbaby from pesky pests. A purr-fect choice for cats and kittens, this collar starts to kill existing fleas on cats quickly, and then it continues to work for eight months. The collar is non-greasy and odorless. Since it kills fleas on contact, they don’t have to bite your cat to die, so the collar helps to keep your kitty comfy.