I think the "I" is meant to be a roman numeral
But a letter on our keyboards none-the-less.
Roxon Vs Rasant: Roxon is the gen 4 tensor sponge, very fast and bouncy. The new version with a grippier topsheet is called Plaxon. After gen 4 (eg: rasant? Not tried it myself), the ESN sponges in general became less springy, more dense and more controllable - more like Tenergy.
I know people who still play with gen 4 sponges (Plaxon) and it's fine.
NextLevel was at one stage playing with Omega V Asia and thought it was the closest ESN rubber to Big Dipper. The ease of arc variation was one of the strong aspects. You'll have to ask him for more info.