Nitrox:

I have used the almost identical Doctersight (http://www.analytik-jena.de/de/DOCTER/Produkte/Reflexvisier__230/). Those types of sights are the best for shots on moving game in my opinion because you perceive the aiming dot just like iron sights (meaning no visual distraction from a scope). Those also sit as low as iron sights, which means they are perfect for doubles that are set up for irons sights rather then scope in respect to stock design). Certainly quicker sight aquisition then scopes or aimpoint devices. First time you try those on a gun will make you smile.