Size (Snap Hook) Overall Length: 40mm (height) x 24mm (width) Inner Diameter: 8mm (height) x 21mm (width) Wire Diameter: 2mm The included backpack buckle is the right size to be used in combination with the snap hook. This size allows for 20mm wide tape to pass through. Since the snap hook and backpack buckle are a set, you can create an adjustable shoulder strap. I will be listing unused materials little by little (*´-`) I will be selling them for less than what I purchased them for, so please consider them☆ Bundle discounts are also available. Please feel free to contact me. Although it is a new, unused item, Please purchase if you understand that it has been stored at home☆