The magazine release button fits my M4 perfectly. It attaches easily to the magazine catch and allows for smooth release. However, that is also the reason I am giving it only 3 stars: the button on the left side is too sensitive, releasing the magazine at the slightest touch. Because of this, I lost the magazine many times during gameplay. The edges with the two red markings were too long and protruded too much; I shortened them, and now I don't lose the magazines anymore.