For a standard capacity Samsung toner cartridge, the K603L contains a surprising amount of black toner powder. This makes the running of your ProXpress colour laser printer, with genuine Samsung CLT-K603L/ELS toner cartridges, mercifully simple and great value too.Buying original Samsung toner cartridges (like the K603L) also ensure that your prints look as good as possible and you also minimise the chance of any technical or compatibility issues too. If getting the very best looking prints is of paramount importance to you, then we would fully recommend the Samsung CLT-K603L/ELS black toner cartridge.