16mm bore means 16mm bore (the internal diameter of the shock body).
Kyosho does sell 16mm bore shocks for the st-r (I don't know if they're the same as the st-rr shocks), so the diameter of the CRT shocks shouldn't be a problem.
http://www.amainhobbies.com/advanced...46-04&x=12&y=6
They say you need part number
KYOIF346-04 to mount the bigger shocks.
Not sure about length differences though, I guess you'll find out when you get them.