Recognize this part or "tool" ?

[Cotton Mouth]

I can't figure out what this is for. Hefty aluminum solid cylinder. When I bought my F6B, it may have been in a box of misc stuff from the seller, but I'm not sure. :confused:
914291439144

[jm21ddd15]

Does not appear to be anything I've seen on an F6. Somebody did some good machining on whatever it is.