This selection of Weber Flavorizer bars are the easiest in the Weber product line to figure out.
If your two burner Weber gas grill has more than five Flavorizer bars then this is a good news-bad news situation that you are already probably familiar with. The grill is the Weber Genesis Jr and is a collectible classic. Unfortunately the size of these Flavorizer bars is unique and nobody sells replacements. Your best bet is to head to a metal fabrication shop and have some custom made.
All other two burner Weber gas grills that have side mounted burner control knobs utilize five Flavorizer bars.
Again, the biggest difference in these three products is how long they should last. The enameled Flavorizer bars should last 3-5 year, the heavy gauge stainless should last 10-15 years and the regular stainless will last somewhere in between.
These are the Weber Flavorizer bars for the Weber Genesis Silver A, Weber Spirit 500 and the Weber Spirit E/S 210 grills made prior to 2013.
If your Weber Spirit 200 series grill has burner controls on the FRONT of the grill (2013 and later Spirit grills) then you can buy the three Flavorizer bar replacement set here.