I bought a matrix from a friend . I wasn't aware of the brilliant way they designed the cheekpiece removal for cleaning . I cannot find any diagrams or videos on how or where to place said ball and spring . Money pit Arms solution is to buy a $20 cheek riser collar set and then give them another $10 for shipping . Woody at MPA doesn't answer the phone . Ed's in Alaska hunting moose for three weeks . I can run it without them , but I'd just like to know how to make it run "as designed" . Thanks I appreciate any help