If you’ve got one of the APS MPX’s, Phantom, Ghost, Phantom etc then you’ll be running a Silver Edge gear box.
When you crack the box open you’ll find a piston with a nylon rack, but it has a metal striker plate. Not bad but keep it in mind as thats a wear point for sure. Maybe swap it out for a full metal rack?
The black oring wasn’t the best seal so go drop in a green or brown too.