Twin 1 1/4" SU carbs were stock on Cooper S and most Spridgets and are popular upgrades on many cars. The reason they are so popular is that the design is fantastic- but let's face it people; everything wears out and these carbs are no exception. And twin carbs by their application must be pretty close to the same to operate as well as they should. Most of us have done a quicky rebuild (replaced gaskets, etc.) on our carbs over the years. If you have never done your throttle shafts, jets, etc- it is probably past due! Our Master kit provides all the pieces for both carbs and include such things as throttle shaft and bushes, jet tube, needle & seat for floats, all the gaskets and "O" rings, etc.