TEN-HIGH Linear Rail CNC parts SBR12 12mm, 600mm 23.62inch Fully Supported Linear Rail The material is the 45# high quality steel, Extend the service life of the shaft and the machine. The shaft is case hardened, If you use normal steel shaft,The bearings will be reduce in use process Metal linear bearing, it&#039;s more durable than Plastic linear bearing. high precision and easy to mount &amp; dismount. Move smoothly without deflection, minimal wear and low noise.