Put this on my G&G M16 A3 yesterday (well, now its an M16 A4 :D). Very solidly constructed, simple installation, literally NO modification needed for this gun. Let me give a brief explanation on how to install, in case anybody is wondering how difficult it is (which it isn't):
Pre-install: Remove your hand guards. Unscrew your flash hider, knock off your front sight, and unscrew/remove your delta ring assembly. (If your gun has a replica gas tube, you should remove this prior to removing your delta ring, as not to damage it)
Installation: Install provided delta ring (screw down as far as possible for the gas tube holes to line up correctly with the body). Install RIS onto delta ring (threaded, screws on). Tighten set screws. Reinstall front sight/gas block. (If your gun has a replica gas tube, this should be installed prior to installation of front sight/gas block).
HIGHLY SUGGESTED: Get the RAS FIX! This thing WILL I repeat WILL WOBBLE if you do not get any one of the RAS fixes available on this sight. It may seem overpriced but trust me, you'd much rather not destroy your gas tube or have your handguard freely spinning around in the palm of your hand!
-Solid aluminum construction
-Includes all mounting hardware
-Mounts Sturdily to body
-Accurate milspec rails
-Allows user to mount many different accessories
-May add some weight, nothing major
-Paint does not scratch "easily", but if you wack it good on a rock I could see it scraping off pretty easy. Then again...why would you hit your gun against a rock?
-No instructions, but unless you're completely inept at simple tasks you should be able to figure it out.
-Wobbles like hell without one of those RAS fixes attatched. Though with it attatched, wobble is a thing of the past.
I think this RIS is absolutely perfect, these cons are simply me pointing out some things I noticed (with the exception of wobble, but the vast majority of rail systems will do this) . Definitely suggested for somebody looking for reasonably price RIS. Looks very intimidating and feels solid. Great buy.