Dale I sent your question to TFT and this is the response I received back from them;
Hope this helps you,i didn't change anything from their email;
The size of the ball is really pretty insignificant as it does not affect the overall flow capabilities of the valve and it is not a full ball. Technically, we say the ball has a 5.5" diameter. It is the 3.65" waterway at the seat that makes the difference. The jumbo series of intake valves have a 5.25" waterway at the seat.
Answered on 11/16/2016 by Butch