I bought a Magpul Gen 3 precision adjustable stock and put it on over the original Commercial Tube, should have changed the tube to the Mil-spec the commercial was tighter than hell. If you are using the round rifle tube you can get a standard end plate like here on e-bay. It is keyed so it won't spin, the nub should keep your stock from spinning.
https://www.ebay.com/itm/Aero-Precis...72.m2749.l2649