The LMT Ejection Port Cover Spring is an important part of keeping your AR-15 in top shooting condition. The port cover helps to keep dirt and debris out of the rifle and also serves as a convenient way to close the port when not in use. This spring is machined for a precise fit and is easy to install. For less than optimal conditions, an ejection port cover is great for use from dry, dusty conditions to rainy, muddy conditions. Depending on your rifle lower, the AR-15 ejection port cover will not have a place on a sport upper receiver. These typically do not use an ejection port cover or a forward assist. Be sure your upper has an insert for the ejection port cover pin to install a port cover. This ejection port cover spring is for use on AR-15 platforms only.