The HKS Fine Tune Timing Belt is made for high power/high RPM Subaru engines. Belt strength has been optimized and designed to allow stable belt tension even when heat expansion occurs in the engine.
Previous timing belt manufacturing techniques have involved applying pressure from the outside to the teeth. This applies tension to teeth making them weaker. By forming a mold with the correct shape of teeth, to begin with, it allows the teeth shape to be formed without compromising belt strength and can decrease the belt skipping on a high torque engine.
The teeth are made from H-NBR grade rubber for additional strength.
* HKS notes that the material and/or molding method may be slightly different depending on the application.