The Raven TopStop upper receiver cover provides essential protection for AR15 and M4 type upper receivers when detached from the lower receiver. This black polymer cover completely seals the upper receiver to prevent fouling contamination.Raven TopStop Upper Receiver Cover - BlackDesigned to snap on most AR15 or M4 type upper receiversTough polymer construction for durabilityCompletely seals upper receiver preventing fouling in or outStops bolt carrier group and charging handle from sliding outOnly fits uppers that are detached from the lowerEssential for maintaining clean upper receivers during transport storage or maintenance work on AR15 and M4 platform firearms.