EP sizes?

When purchasing filters ( OIII, UHC, etc...) for a C-11 scope what is the best route as far as size. Should one buy the 1 1/4", 2", or visual back mount? What are the advantages/disadvantages of each model?

Well, the 1.25" size is nice if you don't plan on looking at the same "type" of objects all evening. You can switch them out easily if you are going to be jumping around from object to object. I personally like the v.back mounts. You have to plan your observing a bit better though. When I mount my UHC on my SCT I try to hit all of the nebulas, planetaries, etc while it's mounted. Then when I take it off, I mount my f/6.3 focal reducer and hit the open clusters or whatever else I'm planning on oberserving.