On according to production standards: ANSI, GB, API, DIN, JS, etc.
Or according to clients's particular requirements.

Materials: FC20\cast steel, stainless steel, chrome-nickel, molybdenum and titanium steel, titanium and other special materials
Nominal Diameter: DN40~DN1000
Nominal Pressure: PN10~PN16
Connection Type: Wafer
Drive Mode: Manual, electric, pneumatic, worm gear
Applicable Temp: -80~250(Degrees Centigrade)
Applicable Range: Acids, alkalis and corrosive gases