In the photo you can see the new, thinner edge of the wrench mated with the slot in the mandrel screw.
My Dremel came with a plastic case that holds the various bits and the Dremel wrench. That case is always in a drawer at my workbench. I can put my hands on the wrench very quickly anytime I need it. But, the small screwdriver I usually use to change the cutting discs seems to wander around the top of my workbench and even hide under other things. This will save me time I would spend looking for my small screwdriver.