This power pulley is a complete bolt-on kit, including the pulley, bolts, and belts. aFe's power pulleys are CNC machined out of billet aluminum and black anodized for that aggressive look under the M5's hood. This power pulley does not modify factory harmonics or dampening. 

Dyno testing this power pulley produced 5 HP and 6lbs. x ft. torque on the s85 platform, meanwhile 10 HP and 7lbs. x ft. torque on the s65 platform

Pairing each of these with improved tuning will allow for maximum performance.