CMMG ZEROED Polymer Ejection Port Cover Kit .308. Rigid polymer design results in rugged durability cleaner streamlined looks and less weight than mil-spec style dust covers for those builds where every ounce counts. Specifications for CMMG ZEROED .308 Polymer Ejection Port Cover Kit: Manufacturer: CMMG Color: Black Fabric/Material: 6061-T6 Aluminum Condition: New Mount Type: M-LOK Package Contents: CMMG ZEROED .308 Polymer Ejection Port Cover Kit CMMG 38BA686: ZEROED Polymer Ejection Port Cover Kit .308