Johnsons cat velvet flea collar contains an insecticide that kills fleas while also preventing their eggs from developing to avoid re infestations it will protect your cat from flea infestations for up to 4 months it is an easy fitting soft and comfortable collar for your cat that has an elastic safety link so that your cat can easily escape if the collar is caught on branches it is also odour free and comes with a bell to alert the presence of your cat it can be used on cats over 12 week