Love the ISO 2 perm. It is gentle, yet gives lasting curl. I use a medium large perm rod, about 1/2" diameter, no less. Using too small a rod will bring tighter curls, but sometimes that leads to frizz. It leaves no bad smell on your hair.
I have very fine hair that has some gray and has been highlighted? This is the only perm I use. Used to have it done in a salon and this is what they used. The curls are so natural.