piston valve

This is a piston that fits in 2 in pvc for a piston valve meant for a air cannon it has a one way valve to increase performance.
To assemble it you need a: 2 in o-ring, 1 in rubber washer, a large rubber washer and a small spring.
Put the spring on the nubbin in the bottom of hole on the top then put the the solid 1 in cylinder on top of spring. Glue the washer onto to the thing that has a hole going through it then glue it into the hole push it in far enough that the marble is touching the washer but not so far that it can't move. put the o-ring in the groove going around the main object. Glue the washer on to the bottom of the main object