I don't know off hand, But I would call moen and ask what size it is and use a socket.
Never could find a socket deep enough to fit. I either go with the good ol basin wrench or one of those pass through auto trenches if there is enough room.
Or try using a hole saw bit to fit the shaft without the arbor and cut the nut off
I use one and swear by it! Even for the plastic nuts.I can't recall the manufacturer or where I saw it, but was a deep holesaw lookin thing w/a shroud around it (I guess to keep the junk out of your eyes) you chuck it up in a drill..it was made cutting off the faucet nuts...looked pretty handy, if I remember i'll post it..probably easier than dremel?