If you plan on changing stocks to a collapsible one . You will need the whole setup . Stock , buffer tube ,spring and buffer .
As you can see the buffer tubes a very different for a collapsible stock . They are not just a round tube . They have a rail like system that has the locking notch's in it for each position the stock stops at .
These are out of stock right now but it gives you a idea what you need
http://palmettostatearmory.com/index...stock-kit.html