XTech Tactical Adjustable Grip
The grip is strong, well built, and made of the same tactical grade polymer as everything else nowadays. The position is held in place by large teeth that engage between the 2 pieces, with no flex or wiggle once the screw is tightened. You will need to use the screw and wrench that comes with it, as a standard AR-15 grip screw will be too short. This is a great idea, and I think every rifle that comes with a collapsible stock should come with an adjustable grip. I heartily recommend this grip. It's every bit as good as a Magpul, BCM, B5, or any other big name grip.