The Jett style mufflers are 1/4 wave tuned pipes. Super tiger was the first to make one as far I know then Jett and nelson came out with them. The jett mufflers have changed quit a bit on the inside and out side from early days until now. I have about 20 different sizes and but buddy has over 200 and has about every different style made from early on. From the testing I have done on most sport engines and Jetts engines is that a full tuned pipe will only give around 200 to 400 more over the Jett mufflers. that really isnt that much when you look at the convenience of the Jett muffler over the full tuned pipe, with mounting and couplers. I would love to see a small jett muffler for the .10 and .15 size engines.