the ones shown swivel out to 45 degrees i believe. The offset concept itself has been done a ton of times. But the swivel is what sets these ones apart from the other 45 degree sights.
also, they just help you sight in on a target without having to adjust your scope if it is magnified. Since changing magnification on a scope can mess with your zero. I know this is definitely the case on the spectreDR scopes.
They are also good for tracking targets and for quick use in case of a primary optic failure.
In airsoft they are pretty much useless, if you are close enough to have to switch to iron sights, then you shouldnt even need to aim. Just look down the gun at where your bbs are going. 90% of the time i do this anyways, scope is just for looks
also, you can just buy a 45 degree rail segment, or adapter and put standard BUIS on them. No need for the 290 dollar BUIS.
http://www.airsoftgi.com/product_info.p ... ts_id=7981
YOU SIR!!!!...... DO NOT HAVE ANY PANCAKE MIX!