Mesa Tactical's 12 gauge to 20 gauge adapter dramatically increases the number and type of butt stocks that can be used with 20 gauge Remington 870 shotguns. Attached at the receiver in place of the standard 20 gauge stock, this cast steel adapter enables the use of any 12 gauge Remington 870 stock. There are many more options for the 12 gauge than 20 gauge, including Mesa Tactical's Urbino Stocks, telescoping stock adapter kits and even the Hydraulic Buffer system.