A brass olive for 3/8 inch tube compression fittings, the larger sibling to the 5/16 version. The step up in tube size suits fuel feed lines and other runs where 5/16 would restrict flow, common on fabricated hard line fuel systems and larger oil circuits. As the fitting nut is tightened, the brass olive is compressed onto the tube, forming a seal without any need to flare the line, which makes hard line assembly considerably quicker where a flaring tool is not to hand. Treat it as a consumable: fit a new olive every time a joint is remade, because the original has already been deformed to the shape of that particular assembly and will not seal reliably a second time.