I heard Carl Cameron yesterday state that the pellets were "5 millimeter" in size. At 0.2 inches, that's pretty large. I think he mis-stated.
I've heard #9 or 7 1/2 size shot.
There seems to be a lot of puzzlement on the size of 'shot' used. Most posts I've read state it was #8 shot. I've seen a few others that claim *7 1/2 or *9.
Not sure what difference it makes, but that's what I've seen in posts here.
In any event, they're all about half the size of a BB. That should give some reference.