Just a FYI . I installed the Katz -eye screen in the D300. I would have loved Brightscreens 13mm prism one but did not know about it but anyway the split / microprism is nice also. Anyway i got it installed and I can see many places where big trouble can happen. So if you are doing this you are at your own risk but it is not really hard but dangerous. Now i come from doing this many times and if this is your first time and your nervous than don't do it. Get the folks that make them to install them for you. Mine had 2 shims in there and you need to make sure they don't come out the pushing down on the spring to unlatch can slip and scrap the screen and such. So think about this and be careful . Jim at Brightscreen gave me a big warning about the install on the D300 so i want to pass that on from someone that does this everyday. Plus I used canned air to get rid of dust , so I actually installed it than reinstalled it because i had a dust spot between screen and prism. So stuff can happen but you should be aware of that.