Heavy Stainless Steel CollarThe collar locks with a stainless steel allen screw, opens with allen key (supplied). -Keep your submissive in-line and in your control with this Thick Iron Locking Collar. The durable and heavy steel will remain firmly around your submissive's neck, keeping them in place. The collar has one O-rings for attachment to chains, ties or other bondage gear. This Means you can securely lock your sub to the toys of your choice. You can even attach a leash to the collar and lead your sub around and make them follow all of your commands.approximate measurementsSmall Ring diameter: 110mm Ring thickness: 7mm Ring depth: 21mmMedium Ring diameter: 122mm Ring thickness: 7mm Ring depth: 21mm Large Ring diameter: 160mmRing thickness: 7mmRing depth: 21mmXLargeRing diameter: 180mmRing thickness: 7mmRing depth: 21mmO_Ring; 23mm 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.