In one example of the disclosure, for each of a plurality of printers of a printer fleet, identification data indicative of marking agent cartridges installed is obtained via a network. The identification data is caused to be stored in association with a fleet identifier for the printer fleet. A request for fleet installation information with respect to a first marking agent cartridge is received from a computing device. It is determined, based upon the identification data, whether a first marking agent cartridge was previously installed at a printer of the printer fleet. Determination data indicative of the determination is sent to the computing device.