This hose assembly was used on the fuel delivery systems in the late 1970s and early 1980s. Installed on some R107 450SL and 450SLC, W116 450SE / L and 280SE, and the W123 280E and 280CE. Be sure to check your car before ordering to make certain this hose is installed. See image below #12 - Leak off line.
This connects to the fuel accumulator located near the fuel pump and filter on some 1978 to 1980 models
Late R107 450SL W123 280E Factory O.E. FID T-Hose Assembly