For disassembly the piston screw is fully turned back so that a gap arises between knurl and screw; the knurled disc as part of the mechanism is loosened in a multi-jaw collet of a lathe. The cap top can be unscrewed with a piece of leather or bicycle tube, never with pliers, since these destroy the cap top. The feed sleeve with the two slots is unscrewed with a matching assembly key, and the feed driven out from rear to front with a punch; alternatively, after soaking in an ultrasonic bath or in water, nib and feed can be pulled out. The small bore in the cap is a ventilation hole against condensation, which however accelerates drying. The M on the piston screw denotes the nib width Medium. All threads are right-hand threads; the grip section is often firmly glued and should then not be loosened.