Paul it's some plywood that I pocketed with my proto track. Cut the holes just to where the threaded portion on the collets slip in. Then welded a frame up using 2x2 box steel and attached. I put some additional hangers towards the bottom for a place to hang the chuck, spindle liners, etc.
my next ambition is to shorten it slightly so that I can stuff it inside one of those castered cabinets that Sam's Club sells for 2 bits.