2 Per PackageIncludes Flanges; Gaskets; And HardwareHedman's 3-Bolt flange hedder reducers are for use with Hedman Hedders fitted with 3-bolt gasketed collectors. Many of Hedman's newer hedder models utilize a ball & socket style collector. If your Hedman Hedders have this style of collector they do not require a gasket. Available in mild steel or aluminized. These reducers do not have built-in O2 sensor bungs. If you require O2 bungs, we recommend the use of Hedman's O2 Sensor reducers.