Abstract: An improved fastening assembly having application for securing a filter element within an air cleaner and incorporating a novel wing nut construction. As used with an air cleaner, the wing nut is engaged with a large diameter threaded portion of a connecting bolt and acts to secure a filter element within an air cleaner housing, while an outer knob is engaged with a smaller diameter threaded section of the bolt and bears against a cover to secure the cover to a housing. The wing nut is provided with an inner threaded metal section which is molded within an outer plastic wing section. The inner nut portion includes a plastic ring having an inner diameter slightly less than the thread on the nut and serves to seal against the thread on the bolt and prevent leakage of air along the threaded connection, as well as preventing the loosening of the threaded connection due to vibration.