Feature:1. Design of disc: NPS>2, usually wedge flexible gate, NPS<2 are of wedge solid gate.2. Body and bonnet connection: usually, 150lb-900lb are of bolted bonnet, 1500lb-2500lb are of pressure seal design.3. Gasket of cover flange: usually,150lb & 300lb: stainless steel + flexible graphite combined gasket; 300lb & 600lb: stainless + flexible graphite wounded gasket; 600lb & 900lb: ring joint gasket; 1500lb-2500lb:pressure seal design.4. Actuation: usually, handwheel & bevel gear operation.5. Back seating design. Standard:Design and Manufacture: ANSIB16.34, API600, API6D, API603, BS1414 Face to face (end to end): ANSIB16.10, API6D Flanged connection: 2"~24"to ANSIB16.5, 22", 26"~36"to MSS-SP-44 to API605 on Request Test and inspection: API598, API6D Butt welded end: ANSIB16.5