George,

FAI Model Supply has the tan rubber madel exclusively for modeling. Tan II is nolonger available because one of the ingredients used in its manufacture has become unobtainable. The Tan Sport rubber is reported by some to be right on parr with the original Tan I which was still pretty good rubber. At any rate, its the only rubber there is that's good enough for competition and its sold around the world. John Clapp is the owner of FAI Model Supply and hes also a Free Flighter who competes in rubber events.