Flashing Dog Collars are easily adjustable & available in 4 sizes. To activate your Flashing Dog Collar, press the button on the battery pack. With each push, choose from a still light, blink, and flash for safety. LED Colors: White Dimensions: SMALL 13.7 to 17.7 in. long / 1.0 in. wide MEDIUM 15.7 to 18.9 in. long / 1.0 in. wide LARGE 17.7 to 20.5 in. long / 1.0 in. wide EXTRA LG 20.5 to 23.6 in. long / 1.0 in. wide Collars come ready to use with 2 replaceable CR2032 Batteries. Each collar is individually wrapped in a poly bag - 50 pcs per carton