The hardness of a material is itsresistance to surface penetration.Harder materials have more wear resistance,but they are also less flexible.
that is, the Primoflex has an almost purple hue, while the R-1000 has a yellow tint and the Duralene has a very slight blue tint.
The others are similar to their larger versions above.
Master Kleer after 6 months in a loop: The smaller tubing samples all exhibit the same clarity attributes of their bigger counterparts...
Pictures: The following picture shows the 1/2" tubing selection reviewed here.
Note how the tacky silicone like texture of the Primoflex is a dust magnet.