Deluxe Steel Bondage Wrist Cuffs These solid, weighty shackles have slightly rounded edges to allow for longer wear without coddling your slave or sub, and accentuate your control with a clean, almost surgical look. Smooth swiveling o-rings give you free reign to couple the cuffs to your choice of fixed restraint or bondage accessory. A hex key is included to open and secure the cuffs. approximate measurementsInner ring diameter: 70mm Thickness: 6mm Depth: 40mm Comes with Allen Key This product is certified 100% Non-Magnate and medical-grade steel. Beware of cheaper products that are not solid surgical steel but chromed steel or poor quality surgical steel that contains Magnate. Magnate is the ingredient that makes steel rust. We will only include this endorsement on our 100% surgical steel products.