Back pressure valve, Globe type, Single spring & Diaphragm Actuated, Pneumatically Operated, Throttling or OnOff Type Control Valve Accu-Flow Series 77, a Globe Type, Single Seated, Top Guided, Single Spring & Diaphragm Actuated, ThrottlingOn-Off type Pneumatic Control Valve. It is a Top guided single seated control valve provides maximum support to ensure plug stability