Here's a tip: If you have enough money and don't want to risk getting ripped off or unhappy, DON'T BUY A USED MARKER. Period. The person who is getting rid of it is getting rid of it because they didn't like something about it. You probably won't like that same thing that they hated. Unless the person is just getting out of the sport, there is a chance that there could be something wrong with the marker.
If you have enough money, just buy a new marker from a trusted source, so you don't have to go through the headaches I went through earlier.
Duct tape is a lot like the force... it has a light side, a dark side, and it holds the universe together...