A3 Industries Masterpiece Arms Defender Rear Stock Adapter Aluminum. This stock adapter allows the use of A3 Industries's full line of modular stocks Skelestocks or any other stock designed for mounting to a Picatinny(1913) rail. Simple 5-minute installation. Specifications for A3 Industries Masterpiece Arms Defender - Rear Stock Adapter: Manufacturer: A3 Industries Color: Black Gun Make: MasterPiece Arms Gun Model: Universal Attachment Type: Picatinny Mount Type: Picatinny Features of A3 Industries Masterpiece Arms Defender - Rear Stock Adapter 3-slot MAGPUL aluminum Picatinny(1913) rail No modifications to firearm needed Modular design for various cross-platform use Package Contents: A3 Industries Masterpiece Arms Defender - Rear Stock Adapter What firearm models does the manufacturer say A3 Industries Masterpiece Arms Defender - Rear Stock Adapter is compatible with? The manufacturer says that A3 Industries Masterpiece Arms Defender - Rear Stock Adapter is compatible with UniversalA3 Industries RSA040: Masterpiece Arms Defender Rear Stock Adapter Aluminum