Drilled safety wire holes for racing Sturdy 1" wrench nut makes removal quick and easy Metal leaf spring provides a positive seal between element and lid Heavy-duty construction provides up to 550 PSI hydrostatic burst strength* Resin-impregnated filter media provides maximum filtering surface for contaminant removal Inner core provides extra structural support to prevent filter collapse Anti-drainback valve (where applicable) eliminates dry starts, prevents oil from draining back into crankcase during engine shutdown Internally lubricated gasket provides positive seal while allowing easy on and off of filter Rolled threads provide extra protection against stripping