The AVS2 Series Carburetor Calibration Kit #1940 is for tuners looking to custom-tune the performance of their #1901, #1902, #1903 or #1904 carburetor. This kit contains all of the necessary metering rods and jets that will allow you to adjust your AVS2 carburetor either richer or leaner for both cruising and power modes. This kit also includes an assortment of seven pairs of jets, five step-up springs, seven pairs of metering rods, metering rod retaining springs, six replacement hairpin springs and a calibration chart that tells which rod/jet combination to use, all organized in a handy reusable storage case.