The FK has a deeper throat depth (164.6mm) than the remainder of Meiji focus blocks which are 136.8mm. This coarse adjusting focus block can be mounted in either direction and holds any Meiji stereo microscope body onto a machine or for other special OEM applications. The 84.2mm diameter opening accepts all EM Series stereo bodies. It also allows our oblique viewing attachment to spin 360 degrees without coming into contact with the focusing holder.