Since the relaunch of the Meisterstücks in the Classique size, i.e. model 144, various feeds have been used. Initially there were two variants with solid feeds. From the 1990s onwards, feeds with lamellae were additionally used, which enable greater pressure equalisation. With lower air pressure, e.g. on aircraft, fountain pens normally tend to drip. The lamellae of the feed can absorb the ink to a certain extent and so effectively prevent the pen from leaking. Overall at least three feed variants on the 144 are documented; further variants are not excluded.
Related pages on fountainpen.de:
• Montblanc Meisterstück 144 (Classique predecessor): https://www.fountainpen.de/c-montblanc-meisterstueck-144-en.htm