The TopStop cover is expertly designed to securely snap onto most AR-15 or M4-type upper receivers when detached from the lower receiver, providing essential protection during storage or transport. This innovative cover completely seals the upper receiver, effectively preventing fouling from entering or escaping. Additionally, it ensures that the bolt carrier group and charging handle remain securely in place, even when the upper receiver is moved around. With the TopStop, you can safeguard your firearm's components and maintain cleanliness and functionality, whether on the range or in transit. Designed to snap-on most AR-15 or M4-type upper receivers, offering easy and secure installation for a wide range of AR-based platforms This will only fit uppers that are detached from the lower, ensuring compatibility with specific firearm configurations It features tough polymer construction