Just bought a stock can anyone tell me what parts are different from fixed to folding

I finally got my form 1 back and I am changing my SDP to an SBR. I bought a KRSSs take off stock on Ebay that was listed as a fixed stock, it has the shoulder pin screw on the right side a solid barrel with a V that I am guessing should be a spring loaded button and not take up the whole circular indent in the stock. Can anyone take a photo of what comes with the folding stock setup or explain if this may be able to be fitted into a folding stock.

It can. You only need the following:

Button Latch
Spring
Roll Pin

Remove the fixed stock V lug. Put the spring into the button and put it into the stock. Press the button down and drift the roll pin into the top of the stock. Verify that the roll pin has a clear path when you press the button down. The roll pin should go thru all the way in. It prevents the button from falling out.

thank you, just what I needed