What OUR universal is a hosel with a step at the bottom of the bore that allows a .355 to set in the hosel square. Not sure what Ping’s is and they don’t define it as a universal, but they have started making the hosels larger, no doubt. If you ask them all they will say is that their it irons take a .355 taper tip. We really don’t know what they are doing to square .355″ taper tips up. It looks like in the few we have looked at that the inside wall may taper a bit, but a .370 still goes all the way to the bottom. If people ask us, when using a .355 in these newer models, we tell them to shim them. They have always used .355 taper tips in their irons, but they certainly fit tighter in years past.
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.