Doggy Dom's Safe D-Lite LED Light Dog Harness Sizes are smaller than usual so please MEASURE YOUR PET before ordering LED lights can be turned on or off for daytime or nighttime use. 3 modes - fast blink, slow blink and constantly on. User replaceable battery - batteries included. Bright LED bulb & fiber optics. LED bulbs last a long time & don't get very hot, so they do not cause discomfort. 12 inch max chest