This is Pineapple Racing's improved version of the Mazda Special Service Tool. Not only do you save $300 over the Mazda SST, but our version has a much larger, easier to read, 2"(51mm), dial indicator. Our nickle plate version looks as good as it will last. It is easy to adjust the dial indicator for either right or left handed use. It makes accurate inspection the cast iron side plates easy. The kit comes with the base and indicator. A video of how to use a step wear gauge is at : http://www.rebuildingrotaryengines.com/videos/Checking_Side_Housings_Plates