this is a 12.5 and plays very true. the only difference is that when you order, you can specify softball or fielding glove and the softball has a little deeper pocket.
if im not mistaken, the 12.25 inch was only available in the classic series. Unless they have added that to the sig series. But if he has the classic series, the sig series is night and day difference in quality. I have a classic series as well and its been in the back of the closet since the day it came in. Spend the extra $20-30 and get the signature series if you are going to order one.