Probably hardest cartridge to refill is HP C6578. If you've mastered this one give yourself a hardy pat on back. HP color cartridges like C1823, forbearer to C6578, have been a challenge to refillers because of unique design that I'm sure was carefully engineered to thwart refilling.

Conversely and ironically, HP couples this with a black cartridge that is a snap to refill, 51645A and C6615. Go figure. But we still didn't get to easiest one to refill. Keep reading.

Lexmark cartridges have followed same basic designs as HP. You can see a remarkable resemblance in Lexmark 12A1980 and its counterpart 15M0120 to HP's 51625A and 51649A color cartridges. All of these cartridges are a pain to refill but can be done with great success if you know secret, and that is to remove sponges and clean them with warm water before refilling.

All laser cartridges consist of a drum, toner, corona wires and cleaning blades among other parts that include gears and other moving objects. The only similarity that they have to inkjet cartridges is fact that you can refill them. You will not get as many refills from a laser cartridge because there are other parts that will eventually wear out that most people will not be able to replace without some technical skills. Expect about three refills on average from a laser cartridge.

Refilling a laser cartridge is not that difficult. First you need to gain access to toner hopper. You can do this by either dis-assembling cartridge or by using a tool to burn a hole into cartridge right into toner hopper. You re-fill hopper with proper amount of toner and re-assemble it or seal fill hole. This is a rather simplistic explanation because there are so many different styles of laser cartridges and each one will have it's own procedure.