I think you misunderstood me. Both ends are indeed flared fittings but here is a packing nut that is threaded onto the top side of the fitting on the pump end of the fuel line. This an OEM Mercruiser fuel line. The packing washer had rotted out and I needed to replace the whole fuel line assembly and I got to wondering why that extra packing and packing nut is even there if both ends are a flare fitting.