X series has high TSER because of the multi-layered advanced metal matrix composite aka MMC

the VK series and X series are Metallic.


ABOUT METAL MATRIX COMPOSRE (MMC)

The V-KOOL X05 series is a multi-layered MMC stack, which consists of a titanium composite material coupled with a metallic alloy, both sputtered onto top grade PET substrate. The MMC material derived from this titanium composite-metallic alloy combination results in a fusion of high performance materials that improve properties in automotive application in terms of fatigue or wear resistance, thermal conductivity, engine efficiency and others.

MMC is nearly always more premium and value-for-money than the more conventional materials they are replacing. In many instances, MMC using such titanium composite material have been shown to provide a performance advantage over a monolithic metal. Its applications are also found in space systems and high-end or "boutique" sports equipment.