Completely safe for humans and pets this small waterproof device emits harmless ultrasonic pulses which are intolerable to fleas and ticks. Clinically tested the Flea Controller attaches conveniently to the pets collar and is safe for puppies kittens pregnant or older pets. It lasts up to one year and is chemical and toxin free so is ideal for chemical sensitive pets and the environment. Measures approx 1 x 1 (2.5cm x 2.5cm).