Tensioner Arms - Type SE Tensioner systems are a maintenance free option to provide longer service life of chain and belt drives. With chain drives they prevent the polygon effect on the slack side and run tautly and run almost silently and effectively dissipates vibration while reducing wear on rollers and bearings.When used with belt drives aids the belts to transmit a constant torque by compensating for belt lengthening and preventing over-heating and excessive slipping. Sprocket Wheel - Type N