[0.05 lb] It's a rangefinder, clarity matters.

[3 x 2.9 x 0.7"] The quality is Leica excellent. Choosing the correct diopter adjustment for your eye(s) is tricky and can take trial-and-error time. It's best if you consult your eye care professional before ordering. (Remember, the M9 comes -0.5)

[3 x 2.9 x 0.7"] I don't know why the M bodies don't have a built-in adjustable diopter, but after a botched cataract surgery, my eyes were not what I had and not what I discussed with the surgeon. Bottom-line, no distance vision in my right eye. I'm not a huge fan of shooting with glasses on. My left eye has distance forever, so I don't quite need glasses for most of my day, but this lens makes the rangefinder sharper than ever. Great fit; snug and secure.

[-0.5] Nice little item - definitely sharpens things up a bit. Only problem is the cost. Similar products for other brands cost a small fraction of what Leica gets for these.

[-0.5] If you don’t have perfect vision get one of these asap! My vision isn’t bad enough for me to be willing to wear glasses, just slightly near sighted. Before the diopter the range finder patch was blurry at 10-15feet away and I wouldn’t always hit focus at f1.4. After getting the diopter I can more often & easily nail focus at distance at f1.4.
My prescription would be -0.75, so I slightly over corrected with the -1 and have been super happy!

[-0.5] I own a Leica MP film camera as well as the Leica M11-P digital camera.
Thanks to this diopter I can now focus my rangefinder cameras in lightening speed.

[-0.5] This diopter makes it possible for me to use the Leica M 10 Monochrom without glasses. It screws in over the eye piece. Make sure you screw it down tightly. The first time I used it I had the camera round my neck getting in and out of the car. At some point it became unscrewed and, fortunately, I found it in the car seat. Now I check it before each use to make sure it is securely screwed on tight. At $195 I think this is a bit over priced, but it's Leica, right?!

[-0.5] My new M11 Monochrom lacks a diopter adjustment. This little item lets me shoot without my glasses. It screws right on and works exactly as I’d hoped.

[0.05 lb] The ring seems loose on my m6 but it stays put. Does its job in compensating for my bad eyesight.

[3 x 2.9 x 0.7"] Not much to say. Pricey as always but gets the job done.