I've been working on a job that requires a lot of wide angle use in dark interiors and have been having a fit focusing the camera, often having to resort to Polaroids to check the basic composition after guessing on the ground glass. Not much fun and really, really slow to say nothing of the expense of the additional Polaroids.
I just bought, installed and tested for focus a Maxwell screen for my Ebony camera and it is absolutely wonderful. The screen dropped right in, a perfect fit, and is at least a stop brighter than the factory screen - maybe more. Bill Maxwell is a pleasure to deal with. If you need or want a great fresnel for your camera I definitely suggest you look at a Maxwell.