Reluctor Ring Jig(GM 5.4 & 5.7) ALL STEEL CONSTRUCTION features 2 indexing dowels to properly align the reluctor ring when installing it on the crankshaft. 8mm Indexing dowel is attached to the fixture by an exterior tang. It can be adjusted for depth to accommodate a variety of popular flange depths. The dowel fits only the 8mm hole on the reluctor wheel. The Interior Indexing Dowel Pin is designed to fit into the dowel pin hole on the crankshaft. It is adjustable to accomode different depths. The combination of dowel pins give very precise alignment of the reluctor wheel and crankshaft. US Patent No. 7,716,827