Yes, the cheap-o kinds that no one likes and that degrade IQ. The kind that screw into the front of the lens (not a teleconverter), 2x or 2.2x or 1.8x or whatever and are made by Merkury/Bower/etc. I just want one for a particular setup I'm testing. Needs to be at least 72mm in the rear thread diametre, the part that attaches to the lens.