Butterfly valve D71X-1.6C, DN50, there is no difference between C and no C? What do you mean by "concrete"?
D stands for butterfly valve. 71 represents the clamp type, X represents the sealing surface material, and 16 represents the valve to bear the pressure 1.6MPA, C position is the valve body material code, omitted to represent gray cast iron valve; C represents the valve body material is carbon steel.
The C indicates that the material is carbon steel and does not indicate cast iron (generally omitted)
Front is the same, there is C refers to the body of the material is carbon steel, without C, usually refers to gray iron (cast iron is more common, so are generally omitted)
