First, it was just my expectation. I'd never run into any instructions that didn't tell me that much detail about the tool to use. Second, it didn't fit any of the wrenches I had. Had it given me the size of the wrench to use, I would just run to a nearby hardware store to pick the exact one I need. Of course, I can easily bring the part with me to try and find the right size at the store, but as you may have figured already, I am lazy...