Dell makes standard and high capacity inkjet cartridges for some printers.
The Dell MK990 (Dell series 9) is the standard capacity version BLACK of Dell MK992, which is high capacity version, while the Dell MK991 is the standard capacity version for COLORS and Dell MK993 is the high capacity version. All printers that uses Dell MK990/991 accepts also Dell MK992/993. High capacity is always more value for money, so for a small price difference, the ink and page yield is substantially more.