Gray Ops CNC Aluminum MPA Matrix/ESR XL Rail Black. Textured Top for Maximum Gripping while driving your rifle. Multiple Flush Cup locations for accessories such as the ''Sikes Clutch''. Specifications for Gray Ops CNC Aluminum MPA Matrix/ESR XL Rail: Manufacturer: Gray Ops CNC Color: Black Fabric/Material: 6061 Aluminum Gun Type: Rifle Features of Gray Ops CNC Aluminum MPA Matrix/ESR XL Rail Machined from 6061 Aluminum Black Anodize Hard Coat finish Each insert has 2 built in flush cup locations (4 total per pair) for each sling and accessory attachment Package Contents: Gray Ops CNC Aluminum MPA Matrix/ESR XL Rail 2x Inserts Gray Ops CNC GO-SRAXL-MX/ESR: Aluminum MPA Matrix/ESR XL Rail Black