Having previously lost a much-loved cat some years ago, I was reluctant to let my two young male cats out without a tracking device. After extensive research, I invested in PetTracer collars for them both. Unlike other products on the market, the collars are light-weight, slim-line, gps/radio tracking system that is safe for animals, and with a long battery-life (up to a month power). I can monitor their movements, detectable inside buildings as well as outdoors, which brings peace of mind, knowing that if either of them becomes trapped inside a shed/outhouse/property, they can be easily located. For location in the dark, a light can be activated remotely on the collar. PetTracer is a first-class product, well-worth the investment!