Sig Cross stock on one of the sig folding 1913 adapters. The stock folds on the Cross but doesn't come with a 1913 attachment. The stock secures with a sinlge screw and has the same interface as the other sig folding options (kate moss, minimalist, minimalist plus) so you could swap them out. You can't put a different stock on the Cross because of the channel cut in the top of the stock for the bolt. I was just trying this out. This setup saved 7oz over a gen 1 magpul PRS and gives a litte more adjustability and folding (left or right).