Description Reviews The MINI Cooper Belt Tensioner keeps the proper tension on your belt to make sure that your crank pulley, air conditioning, alternator, and supercharger are all functioning properly. If you do not have the proper tension, your belt could slip or wear unevenly. It is very common on the Gen 1 MCS models for the small shock to lose its oil over time or for the bushings on the shock to come out. If any of this happens, the belt tensioner loses its grip on the belt, which can result in belt slippage. This belt tensioner is almost the same as the MINI part number in every way except the black hard coat on the pulley is not there and they mill off the MINI part number. Other than that, all the other casting marks are the same. An excellent pulley that we have been using here in the shop for a long time that has been proven to last as long as the original and save the customer money at the same time! 1 Review 4 tensioner damper Posted by Martin Brenneke on 13th Jul 2016 The tensioner was perfect but there needs to be a way to just get the shock made by stabilus. Most of the time this part does not keep it's damping effect and lets the belt slip.There must be some company that make a product that is similar and would meet the same specs.