Certain examples relate to mixing and/or supply cartridges for printing apparatus. One example implementation includes a reservoir to receive printing material from a printing apparatus and to return the received printing material to the printing apparatus. A storage medium stores a reservoir printing material level parameter indicative of the amount of printing material in the reservoir; a recirculation cycle counter indicative of the number of recirculation events experienced by the cartridge; a maximum recirculation cycle parameter indicative of the maximum number of recirculation events that may be experienced by the cartridge.