[goldentrigun]

From what I remember there were only two brands which needed the drm tool to change the threading. ICS not being one of them. If you did have problems though all you do is have to work the rail on and off a few times with some light lubricant and you'll re work the threads that way. I've done it before to fit a rail on to my g&p upper.

All that being said you should be able to fit any 12in RIS on there. Stay away from the Matrix spr kits. They're trash.

 

[goldentrigun]

Yeah, from what I read here
http://www.airsoftcanada.com/showthread.php?t=70948
you might have a few problems but it seemed not to happen with every one of them. If you want you could buy that DRM tool but it seems kind of silly to spend that money on it if you are only going to use it once. I was happy with spending some time reworking the threads by hand. Just when you do it make sure to clean the threading on both pieces every time you work it on farther.