The trigger housing is made from 6061 T6 aluminum and anodized black to create a weather and corrosion resistant trigger. To produce maximum lubricity during trigger performance, the hammer is made from S7 tool steel, heat treated, and NP3 coated. Both the trigger shoe and disconnector have been machined from billet A2 tool steel, heat treated for durability, and carbo-nitride coated for an effortlessly smooth feel.The Timney replacement Two-Stage Trigger for HK MP5 Semi-Automatic Variants utilizes your existing rifles ejector lever, ejector spring, and the ejector axis pin that are matched to your rifles chambering. Keeping with Timneys honored commitment of listening to their customers, the HK MP5 Semi-Automatic Variants Two-Stage Trigger does not require a gunsmith for installation.