The Mepro MX3-F is a 3X power magnifier that attaches to the Picatinny rail immediately behind the reflex sight. The Mepro MX3-F has an integrated push-button mechanism that allows it to ride to the side when not needed. Both models can be configured for the right side or left side ride when not in use and will not interfere with the weapons operating system. Simply flip it into position to engage for longer distance shots without having to re-zero your rifle.