choker collar for dogs Size : Medium Size -(15" - 20" Neck) ,Large Size(19" - 24" Neck), X-Large Size(22" - 28" Neck), You can use a soft measuring tape and measure around dog's neck and leave space for 2 FINGERS to slip between the tape and neck. The perfect martingale collar for dogs in Training or everyday Life. We have different sizes and colors for all dogs.