Carbolite tubing was first introduced on Peugeot's lower-level racing-style bikes having brazed lugs.

It was a significantly lighter tubing than their previous high-tensile tubing as used on their U08 through U010 frames, and as such they no longer spot-welded the cable stops onto the now-thinner tubing but brazed on new barrel-shaped cable stops instead.
Later on they used Carbolite tubing for making their unique lugless frames, which were lighter yet by virtue of their losing the lugs.

My first-year 1979 Carbolite U09 carries the Super Sport moniker of that one year, and sort of lives up to it. It is a great-riding bike imo, with far more-sporting geometry than any previous U0-series bikes. I think of it as "a Super Course with 1-degree steeper angles", again it is an altogether different animal than any that came before it.