Thin Micrometers 9S55 are adjustment screws of very high precision. You mount the micrometer on a Ø8 hole. You clutch 9S55 with your own fixing screw. 9S55M has an extra thread and a fixing nut. You tighten the nut from the opposite side.
Ultra Low Profile Steel Translation Stage 7T164-10 with 9S55M-10 installed.
Micrometers with aluminium handle have -AL at the end of the code. Example: 9S55M-10-AL