Tantus Silicone O-Ring Harness Set is compatible with any harness that takes an O-Ring. Set includes six different sizes to accommodate your Tantus Toy of choice. Do not use O-Rings on penis. this is for toy use only. Harness compatibles. when O-ring is used. Safe for your body: Made from Tantus own unique formula of 100% ultra premium Silicone. Easy to clean: Eco-friendly. Hypoallergenic. Hygienic. Boilable. Bleachable. Dishwasher safe. Diameter smallest to largest: 1.2 inches. 1.48 inches. 1.74 inches. 1.97 inches. 2.22 inches. 2.5 inches.