Used stock in great condition decided to use the folder. $125 shipped discreet PayPal. These are are $220 new . Convert your MCX/MPX pistol to a registered short-barreled rifle (SBR) with the Sig Sauer MCX/MPX Collapsible Stock. Adjustable to your liking, these Rifle Stocks by Sig Sauer offer three different lengths of pull so that it fits comfortably into your shoulder. The Sig Sauer MCX/MPX Telescoping Stock is also incredibly easy to install so there's no professional gunsmithing required. Having a collapsible stock makes stowing and transporting your MCX/MPX a breeze, and it's just as tacticool as it is useful in the field. Enhance your pistol with the Sig Sauer MCX/MPX Adjustable Stock to get a highly tactical SBR.