E450 Rear Brake Pad Replacement - long post w/pics

I wondered why I'd gone out and bought a metric socket when the english ones will usually cover in the larger sizes. I went back out with 13/16" and 7/8" six-point Craftsman sockets. The 13/16" will just tap in place and would have done the job. I think 7/8" would slip at the torque the fastener calls for. I probably bought the 21MM to have the exact tool in my "travel" tool box.
Props to Bryan. He was able to quote 21MM for this job, apparently from memory.