Gray Ops CNC Steel MPA Matrix/ESR Rail Black. Side Rail XL - Steel Specifications for Gray Ops CNC Steel MPA Matrix/ESR Rail: Manufacturer: Gray Ops CNC Color: Black Fabric/Material: 6061 Aluminum Gun Type: Rifle Last Chance: Yes Features of Gray Ops CNC Steel MPA Matrix/ESR Rail Machined from 1018 cold rolled steel Black Nitride finish for superior corrosion and rust resistance Each weight has 2 built in flush cup locations (4 total per kit) for each sling and accessory attachment Package Contents: Gray Ops CNC Steel MPA Matrix/ESR Rail 2x Weights Gray Ops CNC GO-SRSXL-MX/ESR: Steel MPA Matrix/ESR Rail Black