... ,BSPT 3.Can relieve pressure automatically. 4.Long service life. A21H Spring Low Lift Thread Safety Valve:Descriptions:1.A21F ... , A21H-C type are used for the equipment or pipeline of ... ,160P15820/M24×2G1"445010026120825/M33×2G1"445010026125828/M36×2G1"4450100285 A21H Spring Low Lift Thread Safety Valve