Hi,
Why changing ferrules?
Are they damaged or you are doing a reshaft with these clubs?

For the ferrules, they are .355 tips and tapered. Titleist will not sell the ferrules.
You have to mesure the length and the wide size with a caliper.
On Ebay, there is a seller specialized in ferrules that is located in USA. If I remembered correctly, the name is « Grail ». He sells very good quality ferrules. And he have a good variety of sizes.
The delicate process after installing them is turning them. You do not want to have gap or step between the ferrule and the iron’s nozzle. This part separate the professional and the others.
Experience is helping a lot. You want your clubs perfects!
Best regards,

Yes but not sure why you would want to just replace the ferrule. Usually that is done when re-shafting. It's a lot of work if you're just wanting to replace the ferrule. You have to remove and re-epoxy the shaft to the head.
As for the ferrules, you need to get the same size as your shaft tip, and then you have a choice of shorter or longer. Any club accessory supplier should have a variety.

Just remember, anything you do to alter the original build will void the warranty so I would always hold off until the warranty has expired first. Good luck.