| CPC E04H 12/2284 (2013.01) [E04H 12/2238 (2013.01)] | 17 Claims |

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1. An apparatus comprising:
a hollow tube comprising a wall having an outer surface;
four fin members, each fin member having a quadrilateral shape, wherein a respective first edge of each fin member is attached to the outer surface of the wall of the hollow tube, and each fin member extends radially away from the outer surface of the wall of the hollow tube; and
a quadrilateral prism member surrounding the hollow tube and the four fin members, wherein a second edge of each fin member is attached to a corresponding edge of the quadrilateral prism member, wherein two adjacent fin members are connected by two other edges of the quadrilateral prism member.
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