Product review (3 stars): Good Replacement for JennAir Gas Stoves...but buy extras - you'll need them
I'm disappointed that these are only available in plastic.  My stove is only 7 years old and I've had to replace them twice already.  The plastic shaft always cracks leaving the dials loose or falling off the stove.  For a high end stove you would expect jennair to have metal dials - but these are the ones that Whirlpool apparently uses on all the models from low to high-end.  Just buy extras - you'll need them.