For those who already know what this is, good for you. I missed out on this silliness back in 2012. For those like me who have not seen this before, this is a double finger trigger. You may be scratching your head as to why someone would want this on their AR15. The double finger trigger actually comes from the Paintball world. You alternate each finger to pull the trigger and you can get a rather quick rate of fire with a paint ball gun.
Not sure how well this will work with an AR but I suspect it didnt fare well since they are no longer made. However the owner of the AR above put it on a select fire lower. He had to modify it to work with full auto. He did it as a joke.