I am pretty sure from what I have learned on this forum, PB measures 21 inch diameter cooking surface. They call it 24 inches when they measure the outer diameter of the ceramic.
Still bigger than the classic, has almost 700 inches of cook space with the 2 racks included...
Measuring round grills and kamados by their inside diameter at grate level has always been the industry standard. For some reason the suits at Pit Boss have chose to market their products using deceptive specs. That should trigger a red flag alert right there to any intelligent person. They claim their 22 (whatever ever that means) has a 560 sq. inch cooking surface. Kamado Joe's 18 has 508 sq. inch surface. That's only 52 sq. Inches less than a kamado that is marketed as being 25% larger.
I have seen these Pit Bosses and to even try to compare them to a KJ or BGE is ludicrous. They are in the class of an Auplex or Vision, which IMO is not the quality of a KJ or BGE. Their lower cost them may make them as good of a value as the EGG or Joe, but that depends on what your subjective expectations are. My subjective expectations may be higher (or lower) than the next guys'.
I did not mean to suggest that they were the same quality, but it is a good deal on a decent product. KJ is awesome, as I own a big joe, but I have had issues with the hinge and other minor problems. For $100 more than an Akorn, you can have a decent ceramic grill if you are cost conscience.