I have been using Festo clear P.E. tubing from the start on my 1221's as I found my self always bumping and bending the antennas.

It has the ID: PUN-H-3.0x0.5.......I cut pieces in between the lettering on the tubing. I wasn't sure if that ink could cause a problem.

As I noted previously, range checks on all my 1221/12X setups approaches 100 paces with minimal fades and zero frame losses in over 100 flights.