Earthdog Martingale Hemp Dog Collar, Star Pattern Great for your dog and the earth: Earthdog martingale dog collars are made of triple layer, 100% hemp canvas which is hypoallergenic, resists odors and is earth-friendly. Martingale collars can help prevent escape!: Martingales are "limited-slip" collars that are perfect for dogs with narrow heads that can sometimes slip out of a regular collar. Martingale collars will tighten a little when your dog pulls but when properly adjusted they cannot choke your dog like a slip-collar or choke collar would. Handmade in the USA by Earthdog, a wonderful, rescue-focused small business that we are very excited to support. Easy Care: Earthdog hemp dog collars can be machine washed and dried. They get softer with each washing! Safety Note: We do not recommend leaving martingale collars on unsupervised dogs. Please see our regular hemp collars for all-day wear. Sizing: Measure around your dogs neck with a soft tape measure and add an inch or about the thickness of two fingers for wiggle room. Small: 8"-14", 1" wide. Medium: 14"-20", 1" wide. Large: 18"-26", 1" wide.