To exchange your old legs for the new ones, first completely unscrew the black angle adjustment wingnut and remove the cuff from the old leg assembly. The new legs are already marked as either “left” or “right”, but your old handles aren't. So make sure to note which cuff is your left cuff and which cuff is your right cuff (When the crutches are assembled the handles should point inwards). Then reattach the new “left” leg to the “left” cuff and tighten down the black angle adjustment wingnut. Repeat for the right leg. The old legs then go back in the box. Apply the included return shipping label over top of the original shipping label. Then just ship the box back to us.