I just went to check on the hardness of the Roto-Grip Cosmos polyester ball (It's 80 which is very hard these days) and learned that they had discontinued it!!
I think that 80 was second to Storm's Spare Storm's 84-86. I had a Spare Storm but the feel of that ball was just too disgusting. It felt greasy all the time and I couldn't get rid of that feeling. You don't want that grease/oil on your hands. (I always wipe my spare ball off, just so I won't get the oil, which does not soak into the cover like a resin ball, on my hands.)
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"We get old too fast, and too late, smart."