Nothing beats a good set of heavy-duty stainless steel cooking grills. Some stainless steel grids can be pretty cheap, or just far too thin to even absorb any heat. Sure, 5mm or 7mm grids may exist, but they don't do nearly as good of a job as these 9mm thick grids. The thicker your grills, the more heat they will absorb (and yes, that means your food will cook much more thoroughly).
These stainless steel rod grills are designed to fit the Weber Genesis® 300 series (but only ones which date prior to 2012 and have the side-mounted control knobs). A couple of these grids added to your barbecue and we're sure you'll never have to replace your cooking grids ever again.