Scuba Standard Tank Valve Bonnet Nut Polyurethane 015 O-Ring (10 pcs) [Bonus O-Ring Pick] Tank Valve Bonnet Nut O-Ring 100% Polyurethane Material O-Rings, 90A Durometer (Hardness) Includes a plastic o-ring pick to easily replace your o-rings Preferred Material For Oxygen and Nitrox Compatibility Manufactured and Warrantied by Captain O-Ring LLC