After replacing the pressure regulator because of a stem leak, I observed that the new regulator has a composite bonnet instead of brass. It's important for the bonnet to have UV protection from the sun.
The pressure regulator housing measures 57mm in diameter.
Bonnet was printed with PETG at a layer height of 0.2mm, and was designed using Alibre Design V28.
The author marked this model as their own original creation.