This is a 3cm wide half-check collar for medium-sized dogs. Since it is not adjustable, if you are using a half-check collar, please be sure to compare the following leather part size and chain part size with your current size before purchasing. This is a one-of-a-kind finished product, so please contact us if you want a different size. Leather width: 3cm Thickness: Approximately 4mm (may vary slightly depending on the leather) Head circumference: 37cm ● Leather part size: Approximately 28cm (at the hole position in the photo) ● Chain size: Approximately 12cm (The reason the total does not equal the ordered head circumference is because the chain and leather overlap, and it is calculated as the size that can be put on and taken off the head.) Please contact us if you are unsure. +++++++About Extra+Heavy+++++++ Extra+Heavy is a handmade collar shop that specializes in custom-made collars, including half-check collars and leads, mainly for bulky collars for bull breeds and long-necked dogs like Italian Greyhounds. The website is a Rakuten shop, a Yahoo! shop, and the main store. * You can find Extra Heavy by searching for "collar studs" on Rakuten Shop and Yahoo! Shopping Mall.