Microwave turntable; 15/16" gap all around. I saved this one when I replaced an OTR microwave, but suspect any appliance repair shop would almost give them away. Tempered glass? I didn't wrap it in foil on the first cook as I thought the glass would be easy to clean. WRONG! Actual grime (grease, food particles, etc.) came off readily but the smoke stains are still there.
I use a disposable cake pan for a water dish. Haven't tried it without the microwave tray yet, but by itself it leaves a gap of 2-7/16". I use the charcoal grate from an 18-1/2" kettle (ala BDSkelly) for a diffuser rack, so it's supported well enough. Maybe next cook?