0818.21  0829.17  95619217 5972277 71740977 ATB2240 Tensioners are belt tensioners used in automotive drivetrains. The structure tensioner is mainly composed of a fixed casing, a tensioning arm, a wheel body, a torsion spring, a rolling bearing and a spring bushing, etc. It can automatically adjust the tensioning force according to the different tightness of the belt, making the transmission system stable, safe and reliable.