It's just the factory adjustable folding stock that came on the RPR. I'm not sure if it's Ruger's own design or they had it made for them. I know it's a standard buffer tube, it can be replaced with a Magpul Precision stock or any other type of AR stock very easily. but so far, I really like this one and it's adjustability. thought of putting the Magpul PRS stock on it but it's supposedly a lot heavier