CNC-machined from a premium nickel, chromoly steel (8620), case-hardened and finished with an electroless nickel plating for corrosion/wear resistance and lubricity. Sprockets are drilled and tapped to accommodate late-model lock plate, PART #TPR 100, available separately. Will also fit 86-93 Big Twin models with use of OEM #33344-94 (spacer), OEM #12067A (seal) and OEM #11165 (O-ring). Offset measurement is taken from the face that rests against the mainshaft bearing to the inside of the teeth for Total Offset description. For use with .530 pitch chain. Made in the USA.