I couldn't post a review, so I put it here instead. Bought one set of these for my MX2. I have been using a 1050kv motor with 10x4.7 props and wanted to try these, just for fun. I expected more power but that was not the case, with the 1050kv the 10x4.7 is better. These props are well balanced and come with four shaft adapters with the following shaft diameters in mm: 3.15, 3.9, 4.75 and 6.0. The prop hub is 6.8 mm thick and the outer hub diameter is 13.4 mm. These propellers are very flexible, a little too flexible even. Good value, but I deduct two stars for the overflexibility. Will not be using them, at least not on my MX2.
Are you saying that the adapter rings shown on the picture were not included? In that case, make a support case with HK (you should have gotten the rings as on the picture above) and request them! Don't you have any adapter rings for old/other props that fit?