SCUBA Standard 3/4inch NPS K-Valve / DIN Valve Neck DuPont Viton 214 O-Ring (10 pcs) [Bonus O-Ring Pick] K-Valve / DIN Valve 3/4" (Large) NPS Neck O-Ring 100% Viton Type A Material, 90 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