A connector structure is provided for securely connecting a concentric fuel line having a plurality of tubes to a manifold having corresponding fluid passages in communication with the plurality of tubes. The manifold includes coupling unions having axial bores for receiving one end of each of the plurality of tubes. The connector structure includes mounting holes extending transversely to the axial bores. Each of the mounting holes receives a screw so that the outer edge of the screw is tangentially aligned with a corresponding circumferential portion of the outer wall of each one of the plurality of tubes to mechanically and positively secure the ends thereof in the respective bores.