My dad has an '03 Road King Police. He mentioned he wants to get chrome accents/tips for the 2-2 Vance Hines exhaust on it. He used to have the fishtails, and said he wants to put circular end caps on it, like this -

https://www.harley-davidson.com/stor...25-in-end-caps

How can I figure out fitment, measuring diameter?

 

If you have a dealership close to you, you probably can order them. If its still a guess about the correct size you could get a rough estimate and buy him a gift card. That way he can pick his pipes and be happy😁😎

 

You could probably get a list of tip options that will work on the mufflers by contacting Vance and Hines directly or from their website. A Harley Dealership would likely be able to source them for you, but you could probably buy them for less from Dennis Kirk, Revzilla, J&P.....etc.

I'm not sure the Harley/Screaming Eagle exhaust parts shown in the link would work on V&H mufflers, just something to keep in mind before buying anything.

 

Suggestion: 2019 RK. After 15 years he deserves a new bike. He raised you after all