On the site it says: "Note from Bill of Heavy Sports Inc(March 2004):
When my father, Bill Sr. called and said he had the new 'Super Heavy Grip' at his house, I was pretty excited. When it arrived at my door, I originally was going to call it a HG400 as the spring wasn't a whole lot bigger than the HG300. My 9 yr-old daughter, Amber, who is already a grip fanatic, said, 'Dad, this is too big for a 400. It's a 500!!'"
I keep having an image of a 9-year old girl with Popeye forearms, lol!