Best selection and great deals on Thunderheader exhaust and mufflers. Dennis Kirk carries more Thunderheader mufflers & exhaust systems than any other aftermarket vendor and we have them all at the lowest guaranteed prices. Not only that, but we have them all in-stock and ready to ship today. Dennis Kirk has been the leader in the powersports industry since 1969, so you can rest assured that we have your back when it comes to bringing you the best in Thunderheader mufflers & exhaust systems. With our no-hassle return policy and FREE SHIPPING on all orders over $89, you can buy with complete confidence!