This is a semi fluxture based sample holder. The complete flexture holder was too stiff for user to insert sample. The LN screw at the side gives a clearance of 11.5mm for the sample and then can be tightened to hold samples that are smaller up to 9mm. If you want any lower than this, its better to design a smaller feed through.
The bottom (WHITE) side has 4 holes in which you can put 5mm magnets or 5mm ball bearing in case the base of the microscope already has magnets.
The Hex nut to puch the flexture unit is designed for M4.