I have this one here
The gun doesn't stay locked in very well and it's not easy to remove. It's only held in place by to spring loaded wires that doesn't do a good job. To release it you push the round button, but that doesn't work very well since there isn't enough movement in the wires. I wouldn't trust it wearing it outside my house, that's for sure.
This design looks better and I might have to get me one of those since it looks like a better design.