Simple just press into the backside of the coupler and now you have a correct bore on the coupler to register on the gear and keep the coupler running concentric on the front of the blower drive gear.
Made from billet alum. fits with part #1400-0048. Racer must choose 1.250" or 1.300" sleeve when ordering from drop down menu.
Most SSI and newer large shaft Littlefield blowers are 1.50" register on the gear, Kobelco, Fowler, DMPE 1.300" and early GM, Mooneyham, Littlefield, BDS, TBS, Kuhl and Hampton blowers are 1.250" so racer should measure blower gear with a pair of calipers to make sure what they have before ordering.