I've seen them used and they're another tool in the arsenal but normally when there is enough space for the O-ring to so its thing, the bead Cheetah works too. These can come in real handy for some tires.

I bought the set when a tire shop went out of business, and they have collected dust for 20 years or so. I was about to throw them out but Franz told me I'd regret it, so I hung on to them. Ran into some 10 ply low profile implement tires this year, that the sidewalls were so stiff and the rims so wide, that the Cheetah would'nt flex them up enough to catch a bead. Drug the rings out, lube the soft inner rubber up with tire lube, press them down and ride them up as the tire takes air. Takes two guys to maintain even pressure as it comes up but the beads seated. Not sure what we'd have done if I didn't have the rings.

As I say; One more tool in the box.