Go Fast Bits
2004-2007 Subaru STI / 2006-2007 Subaru WRX 3-piece underdrive pulley kit by Go Fast Bits (2010)
GFB Pulley Kit:
GFB lightweight pulley kits are made from aircraft-grade 6061-T6 aluminium and offer faster acceleration through significant weight reduction on the crankshaft. The effect is similar to a lighter flywheel, and the car feels more lively and willing to rev.
Most of their kits are underdriven, which means the accessories are driven slightly slower to reduce parasitic losses.