Duct

A duct (1) of a foamed blow-molded article that is constituted of a polyolefin-based resin with a bending elastic modulus of 800-1,300 MPa, that has an average apparent density (D) of 0.1 to 0.4 g/cmand an average thickness (T) [cm] providing D×Tof 0.005 to 0.04 g/cm, and that has an outer surface side region (18) and an inner surface side region (19) having an average apparent density lower than that of the outer surface region.