Powerflex Exhaust Mounts use the enhanced longevity, stiffness, and heat resistance of polyurethane to better keep your exhaust in one place.Reduced exhaust movementEnhanced heat resistanceBetter longevity in bad weatherRubber exhaust mounts suffer from all the same problems as rubber suspension bushes, with the added problem of heat from the exhaust system. As your exhaust mounts wear, the exhaust system can flex more and more. As one end of it is attached to the engine via the manifold, this combined with engine movement can lead to premature wear on exhaust components.Polyurethane is not only naturally stiffer, but it is also does not weather in the same way, and is much more heat resistant.Please note - Some compounds are available in standard road compound, and harder black compound. Black compound is much stiffer and will reduce exhaust movement drastically, at the expense of transmitting more noise to the cabin.