This is an optional RPM Threaded Hinge Pin Set for the Traxxas X-Maxx. RPM Threaded Hinge Pins work with stock Traxxas A-arms as well as RPM A-arms, are manufactured from stainless steel and are tough as nails! If you’ve lost or damaged your stock hinge pins, or perhaps you’re tired of losing those tiny hinge pin retaining screws, give RPM threaded hinge pins a shot and never look back! Tech Notes: RPM Threaded Hinge Pins are 4mm x 56mm and work in the outer A-arm hinge pin location. Each kit comes with 4 – threaded hinge pins and 4 – M3 locknuts. Our hinge pins can be used as a replacement for CEN GS025 hinge pins as well but RPM versions use a 3mm locknut instead of a 4mm version. When used with the X-Maxx (using stock or RPM A-arms), some minor modification of the A-arms is required for the hinge pins to fit (see instructions for more information).