The long (approximately 20 nm), thin external structure of the bacterial-type flagellum, which acts as a propeller. [ GOC:cilia GOC:mtg_sensu http://www.ncbi.nlm.nih.gov/pubmed/10572114 http://www.ncbi.nlm.nih.gov/pubmed/12624192 ]
Synonyms: flagellin-based flagellum filament flagellar filament