Foldable @R9/15 Stock Adapter (Gen.4 version ) 2 QD Sling Holes GamePro&oo's Adapter Can't Be Disassembled After It Assembled, It Take Reinforced and Durable Design. Strong Aluminum Alloy 7075 Used,Light In Weight But Very Durable. Produced by High Precision 4-Axis CNC Machines,Top Quality In The Markets. Left Hand Open, Easy Install.