It seems to be a little loose, is there any way to fix it, or is something wrong? Is the ARMS Throw lever not to spec or is the rail not to spec? Is there any way to fix it.

Have you tried attaching the light to another side of yer RAS and see if it fits any better?  I'd say it's probably a defective throw lever mount, but put it on another RAS or the 12, 3, or 9 o'clock rail and find out [:)]

Contact ARMS and they will fix you up.  If you contact Surefire they will say its normal and all M900s do this, which they dont.  The FF RAS is one of the few rails systems that is consistantly in spec.  I had the same problem as you.  The issue is with the friction pad that holds the unit in place that the lever cams on.  I hope that makes sense.  A make shift short term solution is to get out the Dremel and cut a custom rail panel that just barely fits behind the M900.  This will hold the M900 forward against the KAC rail and eliminate slop.  Custom cutting the rails is easy one you get the hang of it, just do it slowly and try getting a few cuts in on the end of the rail you will be discarding before making the final cut.

Just had a problem with my ARMS 22M68 being loose. Sent it back to ARMS and the corrected it for me. Any questions call ARMS first.  I talked to Sharon Swan.

Thanks for your help. I am going to call ARMS today.

Interestingly enough I had a 900A mounted on a SIR 50 and if fit perfectly.  Once I changed to a RAS II the fit was less than perfect.  It wasn't loose, but the throw lever flipped over with very little pressure - much less reassuring than the previous SIR!

I have ARMS throw levers on many KAC, PRI and ARMS rails - never had a problem...