To find the perfect size for your dog, please measure your dog's neck circumference in the position shown on the diagram. These collars have bands of 3M Scotchlite reflective material that provides good visibility to the dog and its owner. The metal ring is durable with large loading capacity and tensile strength to suit even large dogs. The buckle is made of lightweight Duraflex plastic for easy, one handed release, preventing cases of accidental unbuckling. The soft breathable mesh lining with padding is ultra-comfortable. Sizes are fully adjustable for best fit. Scroll down below and look at the product description to find the perfect fit for your dog. Size - Collar Width- - - - -Neck Length 2X-Small 1.5cm or 0.6in 28-30cm or 11.0-11.8in X-Small 1.5cm or 0.6in 30-35cm or 11.8-13.8in Small 2.0cm or 0.8in 35-40cm or 13.8-15.7in Medium 2.0cm or 0.8in 40-45cm or 15.7-17.7in Large 2.0cm or 0.8in 45-50cm or 17.7-19.7in X-Large 2.5cm or 1.0in 50-55cm or 19.7-21.7in 2X-Large 2.5cm or 1.0in 55-60cm or 21.7-23.6in 3X-Large 2.5cm or 1.0in 60-65cm or 23.6-25.6in Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.