Product review (4 stars): Great for my kenmore disposal
I don't have an insinkerator but as far as I can tell this will fit in any garbage disposal hole.  If you have the standard type that is non removable you can just cut out the flaps (you don't want to completely remove it cause it serves as a seal too).  Then this will slide down over the old one.  This insinkerator one is kind of rigid though and sometimes a pain to get food to go into.