The above tube is made to use the SAS3 safety notch. The following tube uses the SAS bolt system as well, but is machined to cosmetically place the safety notch where it was on the originals. It is NOT 20 degree canted, however, so an original turned-down bolt will still not fit. I'm using a selector switch mod that makes the selector act as a safety, so the notch isn't really needed and it looks much better this way