often only 13 ml

Actually, these are the 15 ml cartridge of the type "starter", which is intended for the initial assembly of new printers. The cartridge is the same size as the standard cartridge, only 2 ml are more filling it.
Some vendors can not read well. You will send the standard cartridge with 13 ml capacity and remain 2 ml guilty.

Who on quality emphasizes uncompromising, taking the original - best Lichteständigkeit, no clogged nozzles, no splashes of color.