Summary: My experience is consistent with the positive experience of other reviewers. Purpose of purchase: The K&F Concept Adapter was purchased to use my Nikon & Tamron full-frame lenses (primarily the Nikon 50s and the Tamron 90s macro) on my Olympus OM-D E-M5 (MK 1). Result of the first short test (approx. 20 minutes): The adapter fits 100% precisely and has no play, the aperture grid runs very smoothly (6 audible grids) and covers all aperture values of the lenses I tested, which means the adapter is in the Ability to fully open and fully close the aperture (tested with Nikon G 50/1.4 and Tamron 90 SP VC Macro (F2.8 to F32)). The surface finish is also of high quality (much higher than the price suggests) - one possibility for optimization would be the continuous matting of the inside of the adapter to prevent light reflections. But that's whining at an absolutely high level and not feasible at the price. Such an optimization can also be done later - just search for "dead matt black optical color" there are tips from telescope construction (at your own risk!!). The test was carried out at close range (apartment), ie the infinity setting has not yet been tested - but based on the reports of other reviewers, this should not be a problem. A positive surprise for the "hammer price" (the 2nd this year for a Chinese product) - there are still quite high-quality and inexpensive products on the photo market. I'm curious how the adapter performs in the long-term test - the critical point here would only be a defect in the lens lock, since the adapted lens could then no longer be removed from the adapter.... I certainly wouldn't have afforded the alternative Novoflex adapter because of the use of the "heavy" full-frame lenses on the M5 only makes limited sense due to the weight distribution (the 90s Tamron on the M5 became quite unwieldy without a handle because it was top-heavy) and the M5 due to the lack of focus peaking (I know the "helpful solution") for the use of manual lenses is also only suboptimally equipped. This is not intended to be a criticism of the Novoflex adapter, which is probably even better processed and offers further advantages (e.g. the use of an additional adapter (approx. 100 EUR) to relieve the camera bayonet) but costs 10 times the price and that's it for me then not worth it in my usage scenario. A big thank you also to the other reviewers as very helpful for the product selection. ...and no, I'm not a "bought" reviewer and I'm also pretty "old school" - ie quite demanding and critical when it comes to the general quality of photo accessories.