I had a faulty lens recently, and to rule out the JY-43F as the cause I was lucky enough to be able to borrow a MMF-2 to try out in it's place. Both adapters were fine, and their shape and size were identical (just with different logos). In actual fact, even the external and internal packaging was identical in shape and size, again just with different printing. What surprised me was that the JY-43F feels far more solid than the MMF-2. I thought I'd mention this as probably few people will be in a position to compare, and a common complaint was that the MMF-2 felt flimsy. I don't have the JY-43F on me now, but I suspect that the extra weight might be due to it having a metal body compared with the MMF-2's plastic one. I'll check later. In any case, it was probably an order of magnitude heavier. That said, I've never heard of an MMF-2 shearing with a heavy lens, so perhaps the fact that it's lighter makes it the better choice for lugging around. The JF-43F is also a third of the price, but you might need to return it a few times to get one with a tight fit and correctly machined contacts (I didn't, but I've heard of quite a few people who did).