These are made for racing purposes, and are usually custom designed for top end race engine builders, off the shelf this Harmonic balancer will not always run std pulley belt location. MJRace balancers/dampers are made from the highest grades of materials that don’t break. For Naturally aspirated and turbo engines the crank hubs are made from 7075 aerospace alloy. But in the case of supercharged engines 4340 alloy steel is used for the crank hubs. The accessory drive pulley ratios are mostly between 10% and 25% underdrive. This prevents engine overheating , alternator and power steering failures due to overspeed. These harmonic balancers / crank pulley dampers are made to suit ANDRA requirements and meets sfi rules If your engine regularly sees RPM between 10% and 20% more than standard and you are racing on the track doing multi lap events, using fuel cuts and rev limiters in the programming of your engine, as well as rapid accelleration and decelleration then you will need a race series balancer / damper. If you are running RB Nissan the balancer / damper has no provision for A/C belt The accessory drive pulleys are mostly underdriven and in some models up to 20%. (Consult catalogue). Race Series Harmonic Balancers / Crank Pulley Dampers are bonded balancers created for circuit and drag racing applications. Much of the range is instock while customised Harmonic Balancers / Crank Pulley Dampers can also be manufactured to suit individual needs and specifications. The race series may not suit original OEM pulley setups.