600 Racing is introducing a "glass pack" type muffler for use on the Thunder Roadster. This muffler (available through 600 Racing, Inc.) will be allowed for use on all Thunder Roadsters as of 10/24/07. This "glass pack" type muffler offered by 600 Racing, Inc. will be classified as a stock muffler and be legal for use on Thunder Roadsters as per rule #16, page #32 of the 2007 INEX rulebook.