Sig sauer mcx side folding collapsible stock - SIG SAUER MCX/MPX Telescoping And Folding Stock Black - All NFA Rules Apply STKXFOLDTELEBLK

Easy install.looks great, but getting the dang thing to break loose to fold to the side requires the strength of superman or a screwdriver. I used the second option. Getting the button to work to collapse it also is a bit of a pain, but oh well. Hoping it will loosen up time and lube