Step 6: The Coupler
Purchase a Proflex shielded coupler. Part number 3001-215. It is found in the PLUMBING section of ANY home improvement store.
Insert the ABS pipe in the coupler and tighten snug. The coupler is the rear section of the launcher. Insert the pipe / coupler assemly into the fiberglass tube and mark where it sticks out the front end.
Remove the ABS pipe and cut the ABS pipe so none sticks out past the fiberglass tube.