This is the latest design. The screw is 5/8" long instead of 1/2" it originally was for more strength. There is now an undercut at the root of the screw thread to shift the weakest point of the thread internal to the butt, rather than exactly on the mating line between the extension and the butt. 2.5" just fits in my $20 1x1 tube case from Amazon without removing from the butt. That's what I've been playing with the past couple of weeks. Don't be a gorilla tightening it, it is plastic after all. But I haven't had any issues. I do make sure it's snug every time I take it out of the case.
