Diameter - 12 mm
There are 2 possible lengths when it comes to this part (standard is 7mm for an 8mm thick frame, in some special frames you would need the 5mm for a 6mm thick frame).
Tap - M10 X 1 (standard derailleur hanger's tap)
For those of you who managed to ruin the tap that connects the hanger to the derailleur and are looking for a solution that will save their expensive hanger. For those of you who don't have a derailleur hanger in their bike and have managed to ruin the tap in the frame itself that connects to the derailleur.
How do you do this? Just drill a 12mm (0.472 inch) hole where the tap used to be (frame or derailleur hanger) and insert this piece with the hexagon facing the other way from the derailleur (the hexagon doesn't want to see the derailleur) and screw in the derailleur....you're done.