RIS vs RAS
 

I am in the process of acquiring a G&G M16A3 which I will be turning into a DMR style weapon so naturally the first aesthetic thing I will be replacing in the front hand guards. I have been looking into a couple of things but I have come accross two different items: RIS and RAS. I understand that RIS is just the handguard replacement while RAS actually bolts (or somehow fastens) to the upper receiver. Can anyone suggest any pros/cons to each of these? I can only think that the RIS would be easier to remove/replace if need be but I'm not quite sure.

Thanks!

google is great for this kind of stuff...takes less than seconds to find an answer

http://www.quarterbore.com/kac/kacrisras.html