The Montblanc Generation is a cartridge pen that takes the international standard cartridge. Any cartridge compatible with the Pelikan format will therefore fit, which covers by far the greater part of what stationers stock. Genuine Montblanc cartridges are available, but they cost many times as much and bring no technical advantage; they are only worth buying if you are fond of a particular Montblanc colour.
Lamy cartridges are not an option: the firm uses a format of its own that is not compatible with the standard and simply will not go in. When changing colours it is worth flushing nib and feed through with lukewarm water first, until it runs clear.
The Generation itself is a straightforward everyday pen from the entry-level range below the Meisterstück line, and it was the successor to the Classic series. It writes well enough for daily use, but has little collector value.