Expandable threaded adaptor for threadless shell

A filter assembly, comprising:

• a housing defining an internal volume, the housing comprising a first coupling member formed on an outer surface on a housing first end of the housing, the housing first end being threadless;
• a filter head comprising a first thread formed on a surface thereof;
• and
• an adapter comprising:
• a second coupling member formed on an internal surface on an adapter first end of the adapter, the second coupling member engaging the first coupling member formed in the housing first end so as to removably couple the adapter and the housing;
• a second thread formed on an external surface on the adapter first end, the second thread engaging the first thread formed in the filter head so as to removably couple the adapter and the filter head;
• and
• a segmented section formed on the adapter first end, the segmented section including the second coupling member, the segmented section allowing for flex in the adapter first end to expand to a larger diameter to receive the housing,
• wherein rotation of the adapter into the filter head compresses the segmented section into the housing.