Beaphar Flea & Tick Collar For Dogs is a water-resistant collar that will kill fleas and ticks and prevent further reinfestation for up to 4 months. Flea kill begins almost immediately, but it may take several days for the active ingredient to spread throughout the entire coat. The collar is 65cm long and will fit most dogs. The reflective finish helps your dog to be seen more easily in the dark. Suitable for dogs over 3 months of age.