"Make it easy to keep an eye on your best 4-legged friend after the sun goes down with the Nite Ize PetLit LED Dog Collar Light. This handy battery-powered LED collar light emits a bright light that helps make early morning or late night fun less worrisome and stressful. Easy to use design turns on an off with a simple twist. Durable weather resistant plastic light includes a handy clip for easy attachment to the D-ring on your dog's collar. Runs up to 24 hours on its one 927 3V lithium battery (included). Weight: 5 g. Dimensions: 1.73""x0.97""x0.62"". See your favorite four-legged friend in the darkest night Battery-powered LED dog collar light emits a bright ambient glow Great accessory for pre-dawn or after dark outings Lightweight, weather resistant plastic construction Simple twist activation Runs up to 24 hours Uses one 927 3V lithium battery (included)"