JE Machine Tech A2 Buffer Tube Spacer Black. 81 in Diameter: 1 in Features of JE Machine Tech A2 Buffer Tube Spacer For A1 Rifle Length Buffer Tube To Obtain A2 Length For Newer Rifle Stocks Package Contents: JE Machine Tech A2 Buffer Tube Spacer None What firearm models does the manufacturer say JE Machine Tech A2 Buffer Tube Spacer is compatible with? The manufacturer suggests that JE Machine Tech A2 Buffer Tube Spacer is compatible with AR-15JE Machine Tech TS-ABT24: A2 Buffer Tube Spacer Black