If you stretch out the side rails, it will fit, so it requires a little bit of manual labor. I think someone pulled it against some nails or something previously. However, these grid racks fit perfectly:
Also, this smaller breathable, perforated silicone mat fits on top, which is great for stuff like chicken wings as they won't stick on the metal, but you'll still get airflow underneath - much easier to clean!
I also recommend getting a pair of 16x12 pans with fit-in racks, which can act as drip trays, cooking trays, etc. (these racks only fit in the included pans, which are also great for cooling stuff like cookies!):
So that's my current setup. Costs a bit extra, but it's worth it for the convenience & added capabilities!