Its simular to the Hindsite device. I actually like the hindsite a bit better to be honest. Both work, but in my opinion are not as accurate as a peep is.
I also prefer the No Peep if I had to pick a peepless option. I used one for a few months and now I don't even need it. If I set up a bow without a peep, I just shoot it without a peep and no other aiming aids. Well I use a front sight, I'm not that good

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Paul