I have a aluminum (I think) collapsible stock on my AR right now, It moves around a lot, more than I'd like.  I was wondering if anyone could recommend a good collapsible stock.  I don't have a preference for how many positions as long as it's sturdy as can be.  Thanks.

They all move around somewhat. The best fix for the aluminum type is to make a "shim" (about 1/2" wide, 3" long) that lays in the bottom of the buttstock and is retained via the locking pin by punching a 5/16" hole into the shim in the proper location. Usually .010-.012 brass shim stock works well. I have used this method with very good results! This also works with plastic buttstocks as well.