Review on CPROSP 12g CO2 Adapter: Upgrade Your Airsoft Experience with Reliable CO2 Power! by Tom Roberts

Be careful with this item. Although the description applies even to the MCX/MPX Sig Saur models, it cannot be used with a stock. Unlike standard 88 or 90 gram CO2 cartridges, this adapter, when fully screwed into the rear of the gun, blocks the knob used to loosen and place the stock on the CO2 cartridge. Once the button is locked, the stock cannot be reattached to the weapon. Very disappointed especially as the gun I bought it for is listed in the item description/name which I would consider advertising fake and misleading.