New twin screened high performance very low loss coax, similar to Westflex W103.
Copper braid plus a copper foil, giving 100% shielding.
The disadvantages of this coax is that it is very stiff (compared to RG213) because of it's solid single core centre, plus it is slightly larger (10mm) and so needs the special coax plugs as used on the W103 coax.