makes the barrel come out all the way so if you have two you can switch 'em out no damage totally reversible (if you don't break anything)
P.S. the reason my slide is not on is because its broken
Step 1: Unscrew
take all the screws out of the slide first then pull it apart then take the screws out of everything else then pull it apart when you pull everything apart push the yellow button on the other side and take the barrel out
Step 2: The Barrel
pull the gray pieces in opposite directions to pull an orange piece off the metal rod. pull the gray piece off the front. then unscrew the back of the barrel and pull off. flip it over and unscrew the 2 screws holding the gray and orange pieces on. once this is done pull the gray piece off but keep the orange piece. now screw on the orange piece only and then screw the back on again. push the metal rod through the front and then put the spring on. now push the orange ring on again.