Originally Posted by el twe
ISO and JIS have to do with the angle (?) of the square taper on the BB. Those are the two standards. Basically, if yo go with a Campy BB (ISO), you can use a Campy, Miche, or (I think) Gippiemme crank. With a Shimano, Sugino, or Hatta BB (JIS), you can use a Shimano, Sugino, or Bulletproof crank.
Of course, there are others that fall into each category, but those are the basics. Someone please correct me if I'm wrong.
Close. The ISO and JIS both use a 2 degree taper. The difference is in the width between the flats of the spindle as the taper starts, or the width of the conection point in the crank arm. I believe that the jis taper starts at 12.9mm, while the ISO starts at 12.7mm.