Re: uso butler creek size??
I know this might sound like a little more of a pain, but if I was you, I'd purchase the ones direct from USO. I got a new scope with them and not only are the USO marked, they seem to fit better and are more burly than my old butler creeks. The eyepiece cover looks to be a special fit with an extra flange to keep it indexed and still allow for use of the diopter. The rings that the covers snap over seem thicker than standard butler creeks.
Oh yeah, and depending on the age of the scope, there are different eyepiece and ergo designs which might change the dimensions. (I know for certain on the objective.)