.012" diameter before or after the plastic covering?  If that's for the wire inside the plastic coating then your line will be extra heavy and draggy.  If it's for the wire and the coating, then the wire itself is less than .012.

I wouldn't trust it, personally.  If you're serious about flying control line you can get 1000' of trustworthy line from MBS Model Supply for less than $30.  That'll make you about eight line sets per roll.  Or you can get stainless deep-sea fishing leader off of e-bay, if you're careful about getting the right stuff.  If you really don't want to get the real deal in metal wire, get some SpiderWire at your local fishing emporium.  The combat guys are already using it, and they seem to like it.