[0.3 lb] I bought it to mount Mamiya 645 manual lenses to my Fuji GFX 50R . It works very well. It is just a hollow  tube with no electrical or mechanical connections between camera and lens. It is very well made and heavy. Weighs about 8 ounces.

[3.3 x 3 x 1.8"] Bought this to use my medium format Mamiya 645n lenses in the digital era. Wanted a camera with built in image stabilization as it really provides 2 stops of extra usable shutter speed. Hence the Pentax camera. The adapter does a really good job. It is smooth to install both on the body and on the lens. So far I have been concentrating on my 85 mm f1.9 lens. The results are very good with a creamy Mamiya look to them. The internal light meter works with the lenses, in manual mode, and I have had good success with the required manual focusing, utilizing the cameras built in focus confirmation. So with the conversion factor on this lens I have a 130 mm f1.9 lens with vibration reduction, focus confirmation, and beautiful images in lower light that separate from their background. The cameras flash is also usable as a manual flash and works in a pinch in Scientific mode ie trial & error. This is a great piece of gear and size wise the lenses look good on the camera.

[0.3 lb] easy to mount on camera and lens just clicks right in. not much to it. it just works.

[3.3 x 3 x 1.8"] I have to say that the M645N lenses that I have fit securely onto the adapter without any wobble or movement. The focus ring on my lenses was a bit stiff from lack of recent use however even the expected drag when rotating the focus ring did not produce any movement in either the Pentax K mount or the attached M645N lenses. Fitting was secure and wobble-free, this is a quality product with exact tolerances and great build quality - I also like the fact that the Mamiya lenses attach to the external bayonet fitting as they would on the M645 camera, that is with the lens flanges secured behind the mount - unlike some other adapters on the market - thereby resulting in the aforementioned secure fitting. Highly recommended although I have only used this (so far) on my APS-C camera bodies and have yet to use it on the K1 for some 45 'megapixelshift' resolution goodness !

[3.3 x 3 x 1.8"] Very useful tool. I have a large selection of Mamiya prime lenses which are optically far superior to most 35mm/APS lenses. Along with a soft focus, this is just an amazing lens in itself. Please be very careful with this adapter, nothing wrong with it, but the Mamiya lenses are very heavy and place stress on the Pentax bodies. The bodies were not engineered for this weight, nor should they have been. Everything is manual, so slow down and enjoy the experience.

[3.3 x 3 x 1.8"] I have two of these adapters and the most recent on purchased seems to be a little better than the first with its redesigned unlocking mechanism. I can't see spending a lot more something that does essentially the same thing. Built quality is good and for the lenses I use it with I've had no issues with fit on either the camera or the lens.

[3.3 x 3 x 1.8"] Great seller. Fast delivery. A

[0.3 lb] I tried 3-4 different Mamiya 645 lenses to Fuji G mount adapters, including the expensive ($475) Novoflex adapter. I found this FotodioX adapter the best. Here are the reasons:

#1, It is well made, with a pretty good fit. It is not perfect, but there is only a barely perceptible play. I'd rather have it that way than it being too tight, which would be wearing out either my lens or my camera mount or both.

#2, it comes with its own ARCA-compatible foot for tripod mounting. Don't underestimate this! This is very helpful, especially if you use heavier lenses.

#3, the inside of the adapter is finished well in a dark, non-reflective coating, so I don't have any issues with reflections, flare, etc.

My use case: GFX100S + Schneider Kreuznach 120mm Tilt/Shift for the Phase One XF camera (which is where the Mamiya line eventually ended up).

My only gripe, which is not really a negative: I use the Fuji metal grip that extends the body of my GFX100S and gives me a better grip on the camera. With this on, the tripod foot on the adapter becomes too short - I can't mount it into my tripod without the lower edge of the camera running into an obstruction. So I would need to remove the bottom plate before I can put this on a tripod. I could still mount it with the base plate on, but it won't be centered in the clamp (which BTW, is not a problem, as long as I secure it well). Either way, it is not a big deal, and there is actually a positive side to having a short tripod foot: it leads to better stability. So no complaints.

Net-net: I highly recommend it to anyone planning to use a 645 lens with their Fuji G-mount camera.

[0.3 lb] This is a barebones way to put a Mamiya 645 lens on a Fujifilm X series camera. I was afraid it wouldn't adapt the lenses from my 645 1000S, but it did, and it works like a charm! No circuitry for autofocus or zoom, and the rig is humorously large, but I'm getting great images. Perfect for those willing to devote themselves to a fully manual shooting experience. Fits right, and works as it should!

[0.3 lb] I have use this adapter with a GFX 50R, Mamyia 150mm 3,5 + Mamyia extension tube auto-ext ring No 2 to take macro picture. Even with the added extension tube there are no loose very tight fit. The tripod attachment is solid. I have include a scaled picture. I am very please to be able to use some medium format manual lens with beautiful results.