I just picked up two of these today but as far as I know they are for 19 inch monitors. I don't know if there are different versions for different sized tubes. I'm not sure they work. I'm fairly certain I'll have to do work to one or both of them. however I only need one eventually. I picked it up to go with a donor tube that supposedly is compatible with it, but i'm probably a couple weeks from verifying that
however, if you aren't in a huge hurry or don't find one and one of these will work for you, I'll keep you in mind. my plan is to make sure they both work, and keep one as a spare, but plans can change.