Abstract: Disclosed is a clip for spacing concentric ducts or tubes one from the other. The clip includes an elongated strip of sheet metal bent medially of its length to define a first apex and a pair of segments symmetrical on opposite sides of a plane. Each segment includes a first segment portion extending away from the apex and plane, a second segment portion extending toward the plane and defining with the first segment portion a second apex, and a semicircular flange at its end. The clip is disposed between the concentric inner and outer tubes forming the duct assembly at spaced axial positions therealong. The apices and flanges engage the outer tube and the segment portions engage the inner tube. The clip serves to minimize heat transfer between the tubes, and accommodate thermal expansion and contraction of one tube relative to the other while maintaining concentricity and providing substantially unimpeded flow through the annular space between the tubes.