The Novoflex OMLEI Lens Mount Adapter is the required adapter ring to connect a Olympus OM type camera body to the Novoflex Balpro series bellows system. This adapter ring has the Leica M39 screw mount at the other end, but you will still need the Novoflex #APRO (B&H #NOA35) to go from this OMLEI ring to the bellows itself.
Note: Although the lens will fit physically, access to various lens and camera functions are not guaranteed. No electronic communication is possible between the camera and the lens.
Novoflex OMLEI Olympus OM to Balpro Bellows (Leica M39) Body Adapter