Patent ID: 7740105

Claim:
In an outer tube of an exhaust system part, with a sheet metal being rolled double to form a cylinder having an inner plate and an outer plate, and form an overlapped portion with circumferential end portions of said inner plate and outer plate crossed in the circumferential direction, and being joined at the overlapped portion, the outer tube of the exhaust system part characterized in that a plurality of circumferential communication passages are formed between said inner plate and said outer plate, with tip end portions of the respective circumferential communication passages facing with each other to be apart from each other by a predetermined distance from a peripheral edge of one of said inner plate and said outer plate, and are arranged in parallel with each other along a longitudinal direction of said outer plate, and that at least one portion of said overlapped portion positioned between neighboring circumferential communication passages out of said plurality of circumferential communication passages is joined.