Collar material: Soft nylon make sure your dogs stay comfortable. The metal D ring is chrome coated, shinny and durable wear. The collar does not stretch itself, so make sure leave 2 fingers between collar and dog neck. Please always measure your dog’s neck according to our Sizing Chart - Medium 13" - 16.5" | Large 16" - 19" | XL/X-Large 17" - 20.5" | XXL/XX-Large 19" - 23" | Do not choose the size by dog’s weight or breeds only. This Mid dog collar is designed to fit medium dogs with neck girth: 13"-16.5". YOUR PURCHASE HELPS A DOG RESCUE: For every collar sold, we donate an identical collar to a dog rescue. Dog rescues are in constant need of dog supplies. We donate 1 for 1 for every collar purchase. By purchasing one of our dog collars, you receive a premium high quality collar and you donate one to a rescue. Together we can support dog rescues with a never ending supply of collars.