Guess This Part, Win a Tool

Mystery Part

Vin Marshall

Since we inaugurated Guess This Tool, you've all proven way too hard to stump, so for this week's contest, we're mixing it up a bit and giving you a mystery part rather than a tool.

Again, the first to tell us in the comments what it is we're looking at here with the highest level of precision will win a Stanley FatMax 24-inch Level. Good luck!

UPDATE: It seems as if our use of the word "part" was misleading here. Think part as in "part used in the making of stuff" as opposed to part as in "part of a machine." Also, in reference to @GTO's comment, the hole in the center and the threads go all the way through. Keep up all the good guesses!