Back when we were first making these this was the 2nd prototype unit that was on my personal car. It has around 2500 miles on it but ZERO miles on the new bearings which include 2 new bearings for the idler and one for the crank pulley. The old bearings were taken out for inspection and looked great when removed. New ones were put back in when reassembled. The diameter of the crank pulley is 8 1/2" (4lb). This particular caged pulley has the best of everything...4140 steel 6-pin driver with male hex front cover to stop from over-tightening, 4140 center drive piece with 14mm hex openings on both ends, 6 new bushings in higher durometer rubber, powdercoated cage in silver, double bearing idler. Back when we were selling these, something like this would cost over $1000, im only asking $750. Heres a few pics.