The Ping i525 irons, we believe and what we have measured, are more of a universal hosel now, meaning they can take either a .355 or a .370. A .370 slips right in with no issue and a .355 is a little loose. Not sure exactly what Ping is doing from a stock shaft option standpoint, but you can use either. The .370 fits better, in our opinion and observation.
Britt Lindsey
Thanks for your reply Britt.
I have to say “a little loose” is a big understatement. Just used the calipers and got .378. I’d love to hear explanation of what they mean by universal.