My son has this on his collar auctions..works with anything you need to measure. DON'T KNOW SIZE AND NO TAPE MEASURE? Take a piece of string, ribbon, shoe lace, etc and measure around dogs neck, leave room for two of your fingers to fit under it. Take a piece of computer paper..fold in half lengthwise, fold in half again, fold again..open up and you have 8 1" sections..use this to measure the string, or whatever you used to measure.