THE WA1896 TRACTOR TRACKER "U" BOLT EXTENSION SET IS USED TO MEASURE THE TANDEM AXLES ON TRACTORS IN RELATIONSHIP TO THE FRONT SPRING "U" BOLTS.  THE EXTENDERS ESTABLISH A MEASURING POINT TO THE "U" BOLTS ON FRONT AXLES TO MEASURE TO THE REAR TANDEMS.  AS SHOWN ON THE DIAGRAM MEASUREMENTS "A" AND "D" SHOULD BE THE SAME AS SHOULD "B" AND "C" IF THE VEHICLE IS TRACKING CORRECTLY ON THE FRONT AXLE.  TWO OF THE EXTENDERS HAVE 7/8" THREADS AND TWO HAVE 3/4" TO ACCOMMODATE THE MOST POPULARLY USED "U" BOLTS.  THE EXTENDERS SHOULD BE USED WITH THE WA1877 LO  PROFILE  EXTENDER  BAR AND  EITHER OF THE WA1888 TANDEM TRACKER SERIES FOR STEEL WHEELS OR THE WA1890 TANDEM TRACKERS FOR ALUMINUM WHEELS.