A metallic tubular structure having an inner surface providing a passage for conveying fluid or vapor, an outer surface, a multi-layer, strength-enhanced first end segment, a multi-layer, strength-enhanced second end segment, and a flexible segment intermediate the multi-layer, strength-enhanced first end segment and the multi-layer, strength-enhanced second end segment, the metallic tubular structure comprising: a first inner metallic tubular member, the inner surface thereof providing a fluid- or vapor-conveying passage for conveying fluid or vapor therethrough, the first inner metallic tubular member longitudinally extending the entire length of the metallic tubular structure, the first inner metallic tubular member comprising one or more metallic layers; a second metallic tubular member circumferentially disposed on the outer surface of a first end of the first inner metallic tubular member, the second metallic tubular member longitudinally extending a predetermined distance on the first inner metallic tubular member forming a multi-layer, strength-enhanced first end segment thereat; and a third metallic tubular member circumferentially disposed on the outer surface of a second end of the first inner metallic tubular member, the third metallic tubular member longitudinally extending a predetermined distance on the first inner metallic tubular member forming a multi-layer, strength-enhanced second end segment thereat, wherein each of the second metallic tubular member and the third metallic tubular member form spaced apart tubular members so that the two spaced apart metallic tubular member are not contiguous with one another.