This is a linear colour laser, meaning the four coloured toners are built up on the paper in a single pass, rather than in the four passes that a carousel mechanism takes. When you fold down the front of the machine, you gain access to four slots, each of which takes a toner cartridge,
complete with developer drum. They slide in easily and are the only consumables you need to deal with. This integrated approach makes the physical set up and maintenance of the Color LaserJet 3550 extremely simple.