MUST HAVE! Hard to Find, and Totally Necessary.
If you have a Dremel, you MUST check and replace the motor brushes or else you can end up totally burning out your motor quite suddenly after years of service. (Guess how I know this).

It goes like this: you're cutting along and maybe the housing of your Dremel gets kind of hot. Mine was getting so hot I was getting burns on my hand. (Maybe shoulda paid attention to that). Then, suddenly, the motor just stopped working. Dead tool. That's when I looked down and realized that there are those two plastic screw-cap covers on either side of the switch, with a slot that matches the screw-driver that ships with it. Duh.

I borrowed a manual from a friend who still had hers, and learned that you have to check the motors-brushes and if they're an 1/8" or shorter or if they're worn and pitted, you have to replace them. One of mine was brittle like old bakelite and had to be chipped out with a very fine file (which I broke doing this). The other popped out with the spring like it's supposed to. Once I replaced the brushes the tool worked fine again, but I gather I lucked out and I could have killed the whole thing.

The Home Depots in my area do NOT carry these, though the Lowes sometimes do. But if you rely on your Dremel, I'd say get some with your next Amazon order and hold them at the ready.