Well, I use to do commercial two way.  There are various sizes of hard 
line, all the way from kind of small quarter inch flexible stuff up to 6 
inch stuff used in broadcasting.  Most of what I used was wither half inch 
or seven eights.  The half is fairly flexible, but you have to be careful 
with it, kind of like making a bend in half inch refrigeration coper 
tubing.  It has a solid core and the shield is kind of corigated to make 
it flex better.  Takes special connecters which are a pain in the but to 
install.
73s
Butch Bussen
wa0vjr