I'm just as confused as anyone else about this because I keep hearing this. I'll check it out later, I'm too lazy at the moment.
Yeah, it was too hard to choose between the two. You could imagine why. I don't understand myself sometimes, trust me.
The black one ISN'T thicker! I know for sure, I can just "feel" it. It was worth a try man, I appreciate it though. Screw that haha... and thanks, I feel privileged to have some RooR in my glass collection.
Edit: I'm an idiot and most of you guys were right... the red label is 3.2. Still not sure about the black though!
I am pretty sure black labels are always 5.0's, but I could be wrong. I am not a RooR master like some of the members here. Where are you Trikky?
I am pretty sure a caliper is this thing that looks like rounded tweezers and longer. SO you can compare when it pinches the glass. Although I know for a fact there are many different more useful versions of it. EDIT: here is a wiki link with pics http://en.wikipedia.org/wiki/Caliper