I tried the MD-PK adapter using my Pentax K-1 full frame DSLR with a Minolta MD Zoom 100-300mm f5.6 Lens. I was able to take photographs with it, however, there is vignetting around the outer edge of the photograph. It appears that this adapter only has this problem when used with a full 24mm x 36mm (35mm full frame) sensor; however, it might work well with other Pentax K (K-3, K-50, etc.) cameras with a smaller APS-C sensor. I can use it on my K-1 in APS-C mode without the vignetting problem, which in effect increases the magnification by 1.5x (at 100mm it becomes 150mm, at 300mm it becomes 450mm). The vignetting of full frame is why I am giving it 3 instead of a higher rating; their website should specify this limitation.It is shipped directly from China, so it took 15 days to arrive. It can be tracked all the way to your mailbox, though.It seems to be well built and time will tell if it properly fits the camera so as not to damage its lens contact. It comes in the box shown, but without any instructions. So, one has to sort of use common sense in attaching it and hope for the best.