Messi & Paoloni Ultraflex 7 coax cable is being marketed as similar to RG-213 in performance, but 7mm overall (against 10mm).
There is lots of comment by online experts questioning the claims, and critical of things like the braid coverage, copper foil etc, but without real evidence that it does not live up to specification.
Accepting the specifications for Ultraflex 7 and Belden 8267 (B8267, RG-213) for a moment, how do they compare.
Let's take the loss factors calculated for TLLC and de-construct the conductor and dielectric loss for each line type.
Above is a comparison of the cables.
The stand-out difference is that the UF7 dielectric loss is lower, and that is to be expected because it uses foamed PE against solid PE in B8267.
The conductor loss for UF7 is very slightly lower than B8267. At first, this might seem wrong since the inner conductor of B8267 is very slightly larger, but the UF7 has a dual shield with copper foil, and that might well account for the difference.
The result is that for the frequency range shown, UF7 always has lower loss, but it is significantly lower above 30MHz and that is explained by lower dielectric loss which becomes more relevant as frequency increases.