Switch from single shot to auto from outside the gun. 3D printed in PETG plastic for durability. NO permanent mods needed to the gun, just unscrew the old fire selector and put this one in, I will include a paper clip for you to cut a pin to hold the lever on. See here for video https://imgur.com/gallery/pMj5eaC Message me for more videos or info. Shipping for this item is $3-3.50 for usps first class mail so that is why I charge $8 $4-4.50 for printed part and the rest is shipping and fees