I needed a 922R compliance part for my 4 dozen Russian and Bulgarian 74 mags. I bought a bunch of those US-made copies of the original follower that Cope's sells. Wish these had been available instead - I would love to have bolt-hold-open followers for my 74 mags.
I already have bolt-hold-open capability for my 47 mags because I bought a bunch of those square-backed Chinese followers years ago and ground off the nubs on the inside of my mags so the follower went all the way up to stop the bolt. Flawless function so far with a decent amount of use on each one. I just checked, and they have the same geometry as these new followers so the sides of the follower impact the mag body instead of the front of the follower hitting. But I would have bought these instead of the Chinese followers if they had been available back then. And they have those cool step-downs on the sides so you don't have to dremel anything. That would have saved me a lot of work.