This photo ink cartridge contains 1/3 black, 1/3 light cyan and a 1/3 light magenta. You replace your black cartridge with this photo color inkjet cartridge. It goes in the black slot, not the color slot. When you have the photo and regular color cartridge in your printer it produces better looking photos. Instead of only having four colors to print with (black, cyan, magenta, and yellow) it now has six colors. Photo inkjet cartridges are great for people who print lots of photos or color documents but not recommended for people who print mainly text. This is because the photo cartridge has about a third as much black ink in it compared with a black cartridge. Once this ink is out the cartridge has to be replaced. Even if the light cyan and light magenta sections are full of ink you will need a new cartridge. Printers these days print photos well with four colors but excellent with six colors.