MartinG 4 It is what is advertised. This cutter can only use this cartridge. Be careful when you trim next to hard surfaces because they will make the string break. If you hear the motor running more quickly than usual, then it is because the string is too short, or one side has broken off at the hub. When it breaks off at the hub, it's a little difficult to repair, but it can be done. When you can hear that the strings are getting short because the motor is running too quickly, it's good to tap the bottom button to let the strings go out a little bit longer.Very important, and I think causing the problem from some of the other reviewers, is that when you take the cartridge off, you must make sure that the spring stays on the spindle. If you lose the spring, the whole cartridge will empty in just a few minutes.