Exhaust pipe

An exhaust pipe comprising:

• a double pipe including:
• an inner pipe through which exhaust gases pass, the inner pipe including a first enlarged diameter portion and a straight portion;
• and
• an outer pipe disposed so as to surround an outer circumferential surface of the inner pipe;
• and
• a retention member disposed in a gap provided between the outer circumferential surface of the inner pipe and an inner circumferential surface of the outer pipe,
• wherein the retention member is disposed at least one of a first end or a second end of the double pipe,
• wherein, at the at least one of the first end or the second end of the double pipe where the retention member is disposed, a radial clearance between the outer circumferential surface of the inner pipe and the inner circumferential surface of the outer pipe at an opening of the inner pipe is smaller than the radial clearance in an arrangement area where the retention member is disposed,
• wherein the first enlarged diameter portion is disposed in an area outside of the arrangement area along an axis, a diameter of the first enlarged diameter portion increasing outwardly, and
• wherein the straight portion directly extends from the first enlarged diameter portion and is formed outside of the first enlarged diameter portion along the axis.