Does anyone know the outer diameter of a Sig Sauer factory thread protector SKU: SIG1700276, sold by CDNN as being 1/2"-28 and fitting "the Sig 556 and most 9mm pistols"?

https://www.cdnnsports.com/ar1...mm.html#.W4w-s7gnbIU

If you know the outer diameter, please post, as this is the nicest thread protector I've found to complement an AR I assembled.

Thanks in advance!