Size (Snap Hook) Overall Length: 40mm (height) x 36mm (width) Inner Diameter: 8mm (height) x 30mm (width) Wire Diameter: Approximately 3mm The included backpack buckle is the right size to use with the snap hook. It's sized to fit 30mm wide tape. Since the snap hook and backpack buckle are a set, you can create an adjustable shoulder strap. I'll be selling off some unused materials little by little(*´-`) I'll be selling them for less than what I bought them for, so please consider them☆ I also offer discounts for bulk purchases. Feel free to contact me. Although they are new and unused, Please understand that they have been stored at home before purchasing☆