This machine only throws 12 inch softballs.
If you need an 11 inch softball pitching machine, the Heater PowerAlley 11-inch Softball Pitching Machine is what you want. It ONLY throws 11-inch softballs, however.
The only other Heater Sports pitching machine that will throw 11 inch softballs is their Combo Pitching Machine, which will throw both 11 inch and 12 inch softballs as well as baseballs.