The Timney HK MP5 trigger is factory-set with a two pound first stage and a two pound second stage that elevates the platform so the shooter can achieve the utmost in accuracy. All trigger parts have been expertly designed and precision machined from premium materials to guarantee a lifetime of dependable service. 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 rifle’s ejector lever, ejector spring, and the ejector axis pin that are matched to your rifle’s chambering. Compatible with: HK 91/93 and 94 firearms and their clones. These are SEF / Semi-Auto trigger packs and corresponding safety selectors. NOT Compatible with: HK Ambi/Navy/FBI trigger packs or. These HK trigger packs have competely different internals and thus are not compatible.