Phas-Lok adjusting hubs from Zero-Max provide a fast method for changing the phase relationship of components in a power transmission system. The hubs compensate for required timing changes in a system and provide an accurate, mechanical adjustment within a 24° range (±12°). They eliminate the need to disconnect or remove drive components to reposition or re-synchronize components. Mounted in a system, the hubs provide a reliable position control that does not loosen or slip during equipment start-up and shutdown. They come in three sizes with bores ranging from 1/2 to 2-1/2 in, as well as metric bore sizes, and with a variety of split taper bushings.