The GrimmSpeed Lightweight Crank Pulley reduces the rotational mass of the system, allowing your engine to accelerate and decelerate the rotating assembly more quickly.
Your factory crank pulley is responsible for transferring energy from your crankshaft to your water pump, a/c compressor and alternator. It does this by way of a rubber belt and it does it's job well. The drawback to the factory pulley is that it's quite heavy. Reasons for this include less expensive manufacturing and using the pulley's mass to smooth out 'noise' in the accessory system (NOT to be confused with functioning as a harmonic dampener, which it does not).
75% Reduction in Rotating Mass - weighs 1.1lb vs the 4.4lb OEM pulley
Machined 6061 T6 Aluminum - high quality, precision construction
Hard Anodized Finish - ensures a durable finish and resists corrosion
Removal Tool Mounting - allows the use of the GrimmSpeed Crank Pulley Tool
Factory Fitment - direct replacement for easy installation
2015-2018 Subaru WRX (2019+WRX will need an additional OEM backing piece)