dogIDS Embroidered Martingale Dog Collars - Customized with Your Dog's Information - 9 Size Options WIDE SELECTION: This collar is a perfect for any size of dog and comes in dozens of color combinations! Please refer to sizing information below to determine the best size for your pooch. SIZING INSTRUCTIONS: To determine collar size, please measure your dog&#8217;s neck with a sewing tape or string. Then pick the size range where your measurement is closest to the middle of the range. The collar sizes listed are the range of neck sizes that the collar will fit, as well as the width of the nylon strap used. ADAPTABLE: The beautiful thing about this martingale collar is how well it adapts to rapidly changing situations. When your dog is just relaxing, the collar loosens to provide the most comfort possible. However, if you clip on a leash and your dog begins to tug, the collar instantly tightens to provide you with more control without being harmful. PERSONALIZED EMBROIDERY: Getting your dog safely home is your #1 priority, so this collar comes with room to have your dog&#8217;s name and phone embroidered on the collar in a contrasting color. HIGH QUALITY: This collar is made in the USA from durable, fade-resistant nylon webbing. The side release buckle is made from military grade plastic and will hold under tough pressure. Finished off with a stainless steel D-ring.