These are among the easiest of cartridges to refill. They're as simple as removing a plug, cleaning thoroughly, pouring toner in and putting the plug back.

It is important on this series to clean out any leftover toner still in the cartridge... (you can safely use a vacuum on this particular type of cartridge because there are no toner sensors in the cartridge to worry about being damaged by static discharges).
The reason it's so important to clean this type of cartridge out is that in between copies, the XE60 style machines use a cleaning cycle which draws unused toner from the drum, back onto the mag roller of the toner cartridge. Along with the reclaimed toner comes the potential for paper dust to build up in the toner supply. The symptom which results is that particles get trapped behind the toner metering blade causing tiny deletion lines on the copy. This problem is not unique to refilled cartridges... the Brand New Cartridges can develop the same problem. To help reduce the likelihood of this happening to your refilled cartridge, clean out the cartridge thoroughly. Also, educate your customer to use a good quality paper which won't shed as much paper dust. If the symptom does come up, you can use a tool such as a laminated business card or such, to slide in between the mag roll and the metering blade to temporarily resolve the problem We're told that when a customer complains of this symptom to the OEM... their response is to send the customer a similar tool so they can resolve the problem themselves.