Abstract: A non-return valve for use in plastic injection molding is disclosed comprising an elongated body having a threaded end for connection to one end of a reciprocating feed screw. A first removable valve seat insert is received over a cylindrical portion on the valve body and is in abutment with a shoulder formed on the body. A second removable valve seat insert is also received over the cylindrical body portion and is axially spaced from the first valve seat by a tubular spacer. A ring-shaped valve member having valve surfaces on each end face thereof is disposed between the first and second valve seat inserts. An anti-rotation pin is mounted in the valve body and extends into a keyway type notch formed into the first valve insert. The axial clamping force developed by the threaded connection between the valve body and the feed screw functions to clamp the valve seat inserts and the tubular spacer into assembly.