The M42 screw mount is one of the most versatile vintage lens mounts, used extensively by Pentax, Zenit, Praktica and many other manufacturers from the 1960s through 1980s.
This simple passive adapter allows any M42 lens to be mounted on Micro Four Thirds bodies with infinity focus.
No electronic contacts means fully manual aperture and focus control, but the vast range of affordable M42 glass makes this one of the most useful adapters in the collection.