My Ilford safe light is the model that has a glass back and front, the larger glass being 12" x 10". The unit is designed to be hung from the ceiling, although mine sitts on a shelf. I give the size because I think Ilford marketed a range of sizes, and the"902" refers to the filter type. I use a 15w lamp in mine, because I have a small room. It is certainly marked as able to take a 25w lamp. The important point with any safe light is to do a fogging test with your paper, Ilford publish a useful information sheet on the web that covers this. During testing mine showed no signs of fogging after 15 minutes, which is plenty long enough for me since I do all my processing in a drum. I should mention that the light is connected via my enlarger timer so that it goes off during exposure, if it didn't I would not be able to see the image on the baseboard. Hope that helps. Les Mclean uses two of the same fittings in his workshop, and I think he said he uses 25w lamps in his; it is certaily very bright, and good for a similar time to mine. Anyway it is the testing that is the most important thing - safe lights are not safe for long, no matter which one you use.