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). The GrimmSpeed Lightweight Crank Pulley reduces the rotational mass of the system, allowing your engine to accelerate and decelerate the rotating assembly more quickly. 


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 


2013+ Subaru BRZ 
2015+ Subaru WRX 
2012+ Subaru Impreza (FB/FA Engines Only) 
2011+ Subaru Forester (FB/FA Engines Only) 
2012+ Subaru Legacy (FB/FA Engines Only) 
2012+ Subaru XV Crosstrek (FB/FA Engines Only) 
2013+ Scion FR-S