If I am reading correctly, yes the line is cut to fit and basically held in place on the UGS by friction. HOWEVER, what the difference may be is that there are washers/nut that hold the regulator in place on the m4 buffer (mil/tm) and the air line is basically held in place with no room to move (unless you remove the UGS from the lower receiver in an M4 build.
If that info is useful, I do haveTM buffer and I can supply that.
Maybe a call to p* and talk to tech support to see if they might have drawings showing id/od as well as any other pertinent info?
Usually someone in Engineering that I have spoken to with other questions regarding Kythera.
Cheers,
Adam
