Center Cap mm question

[JT ZR-Won]

Hey everyone, I have a center cap question... I currently have the Callaway Dymags with the large center cap that covers the lugnuts. I do not have any small center caps if I take the large cover off.

Just for a different look I was going to expose the lugs and make custom black "ZR-1" center caps. I've seen quite a few on Amazon but noticed a lot of the measurements are in millimeters. Does anyone know what mm size I would need? I attached a photo of the caps.

Jay