Hard plastic quality grinder mechanism made in Denmark. Finished height of mill approximately 100mm (about 4 inch). Actual shaft length 95mm. Fits in 24mm diameter hole in barrel. Requires recess for 34mm diameter flange set 8mm deep in base. Brass knob has coloured dot for distinguishing between pepper and salt mills (black for pepper and white for salt).
Shaft is 4mm square section aluminium. Grinder is held in by strap in base (screws not supplied)

The image is of the 6" grinder.