I think the last mod I want to do to my M4 for now is enable the collapsible stock. I purchased mine new LY in CA and it came with the “collapsible” stock but a un-notched recoil tube.  Does the C-Stock on my M4 just need a four position recoil tube to enable the collapsible functionality, or is this thing purely for looks and I have to replace both the stock and recoil tube? -Rex