Belt tensioner Fits For: Ford F-150 F-250 HD F-350 Bronco E-150/E-250/E-350 Econoline E-150/E-350 Econoline Club Wagon V8 5.8L The replacement automatic serpentine belt tensioner pulley assembly transports power to the alternator,power steering pump,air conditioning and keeps it running smoothly and effectively.It is designed for vehicles that needs an automatic belt tensioner.The torsional round spring design provides consistent tension for maximum durability Belts、tensioners and idler pulleys are designed to the same life cycle，when one of them is replaced,the othes had likely met their design cycle as well, so it is recommended to replace all of them when replacing one of the parts just wanna avoid to having the influences of other accessories'service life For more detailed assembly information, check out our instruction section. If there is any problem with our belt tensioner assembly, please feel free to contact us and we will solve it for you in time ATPPCCE 90K-38123C (3PCS 38123+38015+K061020) Serpentine Belt Drive Component Kit Fit For Ford F-150 F-250 HD F-350 Bronco E-150/E-250/E-350 Econoline E-150/E-350 Econoline Club Wagon V8 5.8L