CMMG ZEROED Polymer Ejection Port Cover Kit AR15. Rigid polymer design creates a lighter ejection port dust cover with a clean look and rugged durability. You dont have to settle for mil-spec build/upgrade to your spec. Specifications for CMMG ZEROED AR-15 Polymer Ejection Port Cover Kit: Manufacturer: CMMG Gun Model: AR-15 Fabric/Material: Polymer Condition: New Package Contents: CMMG ZEROED AR-15 Polymer Ejection Port Cover Kit What firearm models does the manufacturer say CMMG ZEROED AR-15 Polymer Ejection Port Cover Kit is compatible with? The manufacturer says that CMMG ZEROED AR-15 Polymer Ejection Port Cover Kit is compatible with AR-15CMMG 55BA6C8: ZEROED Polymer Ejection Port Cover Kit AR15