I thought there were only two to date, Metabones and Zhonghi. I've noticed that there is another "generic" lens being sold on ebay. It has no brand markings but from the description sounds a lot like Zhonghi even with warnings about a blue dot. The sellers even use marketing images for the Zhonghi. Two differences though. One, the mounts on this generic lens look better than on the Zhonghi. The Zhonghi has the standard flanges cut in springs like you would find on any cheap ebay lens adapter. The generic uses real clip springs like you would find on a camera. I thought the generics were delabeled Zhonghi lenses but why would they put better mounts on them? The 2nd difference is price. These no name focal reducers sell for $99. One is even listed at $93.50. That's substantially cheaper than the Zhonghi. I've said it before, but I think the price of these will settle into the $30-$40 range. That's where lens adapters with glass elements and cheap TCs sell for.