Fits on a dogs collars with elastic. A few designers have Velcro to attach to the collar.
 
SIZE
Small fits smaller up to 5/8 width collars. They are approx. 3 1/4' X 2'
Medium for up to 1 inch width They are approx 4 3/4' X 2 3/4"
Large fits 1 inch width collars no more than 1.5”. They are approxc. 5 1/2"X 3'