The four of these I received are rather low quality. The thread profile on these isn't symmetrical as it should be for 5/8-11 UNC threads (https://en.wikipedia.org/wiki/Unified_Thread_Standard). One side of the thread profile is angled (as it should be) and the other drops right off. (Visualize a sawtooth wave as opposed to a triangle wave, and you'll get the idea.) Fortunately the side that's angled on mine happens to be the side that will be mating with and applying force to the corresponding threads of the antenna, but it's still disappointing. I had previously purchased (from Jeff Bezos' store) two "CAMVATE 1/4"-20 to 5/8"-11 Threaded Screw Adapters" that were beautifully machined in stainless steel, albeit for about twice the price of these here. Wish I'd just bought more of those.