The 1554-1 is used to calibrate Park Tool wheel truing stands. It is installed into the uprights of the stand, where it simulates a perfectly dished wheel, allowing you to center the uprights and calipers. Compatible with the Park Tool TS-2, TS-2.2, TS-2.3, TS-3, TS-4, or TS-4.2, as well as other truing stands with similar designs.