Size (Snap Hook) Overall Length: 40mm (height) x 24mm (width) Inner Diameter: 10mm (height) x 21mm (width) Wire Diameter: 2mm The included backpack buckle is the right size to be used in combination with the snap hook. It's sized to allow a 20mm wide strap to pass through. Since the snap hook and backpack buckle are a set, you can create an adjustable shoulder strap. I will be selling off unused materials little by little(*´-`) I will be selling them for less than what I paid for them, so please consider purchasing them☆ Bundle discounts are also available. Please feel free to contact me. Although they are new and unused, Please purchase them only if you understand that they have been stored at home☆