Diesel cigar shaped fuel hose

Hello forum, I have just purchased a 1981 300D - non turbo, 100,000 original miles and I am hoping to run Biodiesel, not svo/wvo. In looking over the fuel lines, my mechanic told me that the thick bloated looking line immediately before the canister fuel filter was that shape as a "damper". I haven't seen any kind of chem resistant hose in that odd shape. Is there a specific replacement for this piece or will other hoses serve the same function? Thanks, Dave
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