The Tef-Lok® sealing system not only keeps your fittings from seeping, they will help to prevent your fittings from inadvertently loosening during extreme use. The unique design of the seal protrudes about four thousandths of an inch for an interference fit when tightened and will help in maintaining tension on the fitting B-nut when properly torqued. These fittings should be tightened the same as any other AN fitting being careful not to over-tighten.