This flat idler pulley assembly is an essential engine accessory drive component for heavy-duty trucks. It maintains proper tension on the engine flat belt, stabilizes belt transmission, reduces belt slippage, vibration and noise during engine operation. Built with high-precision bearing and wear-resistant pulley surface, it can withstand continuous high-speed rotation, high temperature and heavy vibration under long-haul working conditions. The pulley undergoes strict dynamic balance treatment to minimize eccentric wear and extend service life. Every assembly passes rotation and load testing before shipment. It effectively solves belt skipping, abnormal noise and premature belt wear, serving as a key replacement spare part for truck engine maintenance.