I have the Hiperfire 24C which is similar in design to the Hiperfire you posted w/ the upper "toggle" springs (great design). Very easy to install following the excellent instructions. Normally, if any given assembly requires additional anti-rotational pins, it will be clearly stated. Unless the instructions state to not use anti-rotation pins, which some do, I go the extra mile and install KNS anti-rotation pins. If you choose to go that route for the 15-22, you must install the pins specific to the 15-22. They are a tad longer than AR15 pins. The Hiperfire has very, very little to no discernible pre-travel and a tiny bit (1mm or so) of reset. The 24 3G (I believe) uses a curved trigger and the 24C a flat / straight trigger with an adjustable, optional "pad". Very smooth operation and no worries regarding the rimfire "light-strike" phenomenon.