This is one of the two electromagnetic Mamiya cable releases available for the RZ67 and Mamiya 645 Pro and Super cameras.
Note! It is also possible to use a traditional screw-in, non-electromagnetic cable release with these cameras. The 645 cameras require a cable release adapter which comes with the body and attaches to the side of the camera. The Pro and Super models use B&H# MACRA645, while the Pro TL uses B&H #MACRA645PTL.