This brand-new belt tensioner with part numbers APV2739, 20487079 and 21260406 suits FH12 truck engines perfectly. It keeps drive belt tension balanced automatically, so as to stop slippage, vibration and strange running noise. It adopts robust spring parts and abrasion-resistant outer shell. The whole unit runs reliably even under extreme heat and continuous heavy workloads. Manufactured in full compliance with OEM standards, it boasts precise sizing for hassle-free direct installation. It serves as a great aftermarket alternative to replace worn-out or faulty original belt tensioners.