RPM Oversized Rear Axle Carriers for the Helion Volition & Criterion are designed to solve several key durability issues. The first and most obvious is bearing life. The stock 5x10mm outside bearings simply can’t handle the loads generated by these beasts! RPM Oversized Rear Axle Carriers bump up the outside bearing size to 5x11x4mm bearings (not included). One millimeter in diameter may not seem like much but that little change nearly doubles all load and fatigue ratings over the stock 10mm bearing! That means better performance, longer life and more time between maintenance periods.