Mysterious Universal Nut

This is an extremely clever precision brass prop that makes possible an incredible close up illusion.
The performer displays a double ended bolt, and a nut. The bolt is of a different diameter at the two ends, with one end of the bolt twice the thickness of the opposite side.
The performer first screws the nut on the bigger bolt, and it fits perfectly. He then unscrews this, and proceeds to screw the nut on the narrow end of the bolt, and once again it fits perfectly.
You may, if you choose hand the bolt and nut to a spectator to examine, and he will not be able to fix the nut on the broader bolt. The nut is just a perfect fit on the narrow bolt, and there is no way it could have screwed over the broad end of the bolt, except by magic !
The apparatus we supply for this is comprised of two double ended bolts, two brass nuts, and instructions. This is a mechanical prop, and does not require sleights to perform.
If you like clever mechanical props, this one is a must for your act, or your collection.