These collars come in: * 1" Extended D * 3/4" Extended D * 1" Ring-N-Center * 3/4" Ring-N-Center. Nite Lite® nylon collars are constructed from two layers of strong nylon webbing. These durable collars also feature the canine buckle, curved to fit the dog's neck for comfort, and floating keepers to keep the collar ends in place. Free nameplate available with each collar ordered. When you select these collars, you will be guided at checkout for engraving information. To select collar size: Measure dog's neck and add four inches. Example: 17" neck will need a 21" collar..