Luth-AR A2 Buttstock Spacer - Aluminum Black. This Butt Stock Spacer by Luth-AR is developed specifically for A2 buffer tubes and can be used on A2 A3(maybe need a little shorter) buffer tubes due to differences in receiver height. The Luth-AR A2 Buttstock Spacer features a rounded bottom with a ridged top so that it can be paired with any line of Buttstocks easily. If you need help pairing that Buttstock to your gun then start here The Luth-AR A2 Buttstock Spacer will only work on A2 A3(Maybe need a little longer due to longer action springs on some A2's ). Specifications for Luth-AR A2 Buttstock Spacer: Manufacturer: Luth-AR Color: Black Additional Features: Aluminum Fabric/Material: Aluminum Package Contents: Luth-AR A2 Buttstock Spacer Luth-AR A2S-01: A2 Buttstock Spacer - Aluminum Black