I'm not sure the material used, but I have used Vise, Prosport and Turbo in mine and my wife's balls. Just me....I like Vise, not sure if it's softer, just like the feel better. My wife, she likes the Turbo. Go figure, that means I have to keep more around of each brand, but I think it's a 'personal' thing, one likes Fords, one likes Chevys, one likes Dodge...for me, it's Vise all the way.
I know this hasn't helped, probably, but just my 2 cents worth.
--------------------
AZ Guy aka: R & L Bowlers Pro
rlbowlerspro@cox.net
www.rlbowlerspro.comSleep is over rated.