Cartridges
Most European fountain pen brands (for example Caran d'Ache, Faber-Castell, Michel Perchin, DuPont, Montegrappa, Stipula, Pelikan, Montblanc, Monteverde, Sigma, Delta, Italix and Rotring) and some pen brands of other continents (for example Bexley, Retro51, Tombow and Acura) use so called "international cartridges" (AKA "European cartridges" or "standard cartridges" or "universal cartridges"), in short (38 mm in length, about 0.75 ml of capacity) or long (72 mm, 1.45 ml) sizes, or both. It is to some extent a standard, so the international cartridges of any manufacturer can be used in most fountain pens that accept international cartridges.
Also, converters that are meant to replace international cartridges can be used in most fountain pens that accept international cartridges. Some very compact fountain pens (for example Waterman Ici et La and Monteverde Diva) accept only short international cartridges. Converters can not be used in them (except for so-called mini-converters by Monteverde). Some pens like modern Waterman pens have intentional fittings which prevent the usage of short cartridges. Such pens can only take a proprietary cartridge from the same maker, in this case the long Waterman cartridges.
Many fountain pen manufacturers have at various times developed their own proprietary cartridges, for example Parker, Lamy, Sheaffer, Cross, Sailor, Platinum, Platignum, Waterman and Namiki. Fountain pens from Aurora, Hero, Duke and Uranus accept the same cartridges and converters that Parker uses and vice versa (Lamy cartridges, though not officially, are known to interchange with Parker cartridges also). Cartridges of Aurora are slightly different from cartridges by Parker. Hero, Duke and Uranus have made few fountain pens that take international cartridges. Corresponding converters to be used instead of such proprietary cartridges are usually made by the same company that made the fountain pen itself. Some very compact fountain pens accept only proprietary cartridges made by the same company that made that pen, for example Sheaffer Agio Compact and Sheaffer Prelude Compact. It is not possible to use a converter in them at all. In such pens the only practical way to use another brand of ink is to fill empty cartridges with bottled ink using a syringe.
International cartridges are closed by a small ball of glass, held inside the ink exit hole by glue or by a very thin layer of plastic. When the cartridge is pressed into the pen, a small pin pushes in the ball, which falls inside the cartridge. The Parker cartridges do not have such a ball. They are closed by a piece of plastic, which is broken by a sharp pin when inserted in the pen.
Pen manufacturers using a proprietary cartridge (which in almost all cases are the more expensive ones like the ones mentioned above), tend to discourage the use of cheaper internationally "recognised" short/long cartridges or adaptations thereof due to their variance in ink quality in the cartridges which may not offer as much performance / or be of lesser quality than the manufacturer of the pen; ink that has been designed specifically for the pen. In addition, cheaper ink tends to take longer to dry on paper, may skip or produce uneven colour on the page and less "tolerant" on lower, thinner grades of paper (e.g. 75gs/m).
While cartridges are mess free and more convenient to refill on the go than bottle filling, converter and filling systems are still sold. Non-cartridge filling systems tend to be slightly more economical in the long run since ink is generally less expensive in bottles than in cartridges. Advocates of bottle-based filling systems also cite less waste of plastic for the environment, a wider selection of inks, easier cleaning of pens (as drawing the ink in through the nib helps dissolve old ink), and the ability to check and refill inks at any time. The Noodler's Ink Company even goes so far as to maintain a "zero disposable cartridge" policy and refuses to issue any cartridges due to their high levels of economic and environmental waste (a single bottle of ink can represent a few hundred international cartridges at between 350% and 780% the cost of similar bottled ink on a volume/dye content comparison depending upon different brand costs). Disposable pen cartridges have been found floating in most ocean trash samples another reason for Noodler's refusal to cooperate with the predominant filling method used by modern pen companies.
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