It's interesting......I normally use Carlton's calls, so the 5/8" frame and I don't even have to think about it. They go in my mouth and good sounds immediately come out without even thinking about it. So I ordered some 5/8" Phelps calls and tried them. Laying one of those over or next to the Carlton's they look identical in size and shape, but I really struggle to get any sounds with them, let alone good sounds. But I tried Phelp's 1/2" frames, and they flow like the Carlton's 5/8".
I've never liked the sonic dome type calls or any of the ones with the raised metal piece, yet the Primos Mini-sonic domes work fine. I tried one of Carlton's new "Native" reeds this year, and I struggle to get sounds with it. Yet it looks identical to his old calls.
It's really hit and miss for me, so I stick with what I know works. I'm just afraid they're going to discontinue them because I like them so much.