Funny, i loved the pressureless balls, which were easily available in the USA (or California at least) in the 1970s and 80s. The brand name was Treton (or Tretron - i think they made a racket also). We would use them for a change of pace - called them "pocket rockets." It helped my big-serving opponents frequently, but almost as often they had trouble controlling their serve, and just putting a (wood) racquet on their serve gave me a fast, deep return. It was fun. Then, in Mexico City, of course, we used to always use pressureless because of the high altitude (6,000 feet; 1,825 meters and higher). Nowadays, it is a mix in CDMX of pressureless and pressurized. the pressurized have to be brand-spanking fresh or it is deadsville. So, i am surprised to hear the comment (was it from Ashe?) that the Pirelli pressureless were so difficult to put away. From the context, sounds like ref. was to Roland Garros. Paris is hardly above sea level, so it seems weird that pressureless would be so difficult to put away. But there is no questioning the long, drawn out rallies at the French in the 1970s. My experience at sea level in California was they were kiss-my-hand easy to put away . . . or to put out the court