There's one for sale on site. No, it's not mine. I have been using one for a number of years, and they are very good densitometers. The aperture is 1mm, which makes reading areas like the dark border of a frame easy enough to do. You can use them to check density for regular silver printing or for the UV processes. They are well-built, professional machines, and I have a manual that I would photocopy if needed. With a few simple tests you can dial in your exposure and development for most photo processes. This is especially useful for newbies who don't know what a good negative for a specific process should look like.