The nozzle does not have punch marks on it like other "Czech" nozzles - the nozzle is not deformed during production. The nozzle is marked with drilled holes.
Number of holes on the walls:
4 holes = nozzle size 0.4 mm
Total nozzle length 21 mm. Thread length 15 mm. M6 x 1 thread
Nozzle size means: Outlet diameter / Inlet diameter