BCO&copy; Lightup LED Dog Collar - Lights up to keep your pet visible at night Colored flashing helps identify your pets easily, and an eye-catching design turns heads Easy to use: simply push the control button to set it to ON, FLASH, or OFF. LED light: run time is more than 72hours. Battery Operated: uses two CR-2032 watch batteries (included). Purr-fect for cats, dogs, bunnies, and others. SMALL: 10 long, MEDIUM: 17, LARGE: 23, EXTRA LARGE: 25