The Geissele Maritime Bolt Catch is designed with the warfighter in mind and will work with any lower receiver designed to accept a mil-spec M16/M4 Carbine bolt catch. The increased surface area promotes ease of function when locking back the bolt or releasing the bolt after a magazine change. In addition, the extended controls add an increased functionality for left handed shooters who no longer have to break their grip to manipulate the bolt catch. Left handed shooters can easily reach the controls using the index finger of their left hand making magazine changes and locking the bolt back much more fast and efficient. Aggressive checkering covers the surface of the levers giving the Geissele Maritime Bolt Catch a textured surface that enables positive feedback to the shooters hand when being used with gloves or at night. Manufactured from properly heat treated 8620 steel and manganese phosphate coated, the Geissele Maritime Bolt Catch is intended to serve as an enhanced mil-spec replacement and assist in giving our warfighters overmatch capability with the M16/M4 carbine platform. Please Note: A mil-spec bolt catch spring, plunger and roll pin are required for assembly and are not included. If the Maritime Bolt Catch is replacing an existing mil-spec bolt catch, please use care when disassembling the component from your lower receiver as you will need these parts to install the Maritime Bolt Catch. Compatibility with billet AR-15 lower receivers is unknown. Please also note that the extended controls of the Geissele Maritime Bolt Catch will partially cover the pin hole for the hammer, a smaller punch may be required to push the hammer pin out of the receiver from the left side, and the hammer pin should only be installed from the right side of the receiver.