I have three external pressure regulators that I used at different times over several years. They are brass, the type that screws onto the hose bib. They restrict flow so I only use them to try to save the hose when the water supply has a very high water pressure.
When I used a water pressure gauge to check, I found that the external regulators let water pressure build up slowly, over hours, in the plumbing system to equal pressure in the supply. In other words, they did not regulate pressure properly. YMMV
2014 Silverado 1500 5.3L maximum trailering package (yes, I'm towing the 34')