The Adams Flea and Tick Collar for Dogs and Puppies kills adult fleas and ticks AND repels mosquitoes for up to 6 months. Two collars in each tin provide up to 12 months of flea and tick control. The collar features an extended-release technology that distributes the active ingredient over six months. The collar is a convenience over messy topical applications that release a high initial dose and last for just one month. Once the collar is applied, the active ingredient is transferred from the collar to your dog’s hair, and then to the skin. Adjustable, one-size collar fits all dogs. Water resistant.