Cilium- and flagellum-specific protein that plays a role in axonemal structure organization and motility. Involved in the regulation of the size and morphology of cilia. Required for sperm individualization, differentiation of the sperm flagellum and tubulin polyglycylation of axonemal microtubules. Localizes in cilia of chordotonal organs in sensory neurons of the antenna. Localizes in small primary cilium composed of a transition zone and a short axoneme. Localizes at the top of the giant centrioles and enriched in the nucleolus of spermatocytes. Expressed in spermatocytes and chordotonal organs in sensory neurons of the antenna. Flies are viable and develop until late pupal stages. Display defects in wing posture and inflation, in locomotion and climbing activities and have a reduced lifespan. Males produce immotile sperm and show defects in sperm individualization process within cysts. Display defects of polyglycylation incorporation in sperm axonemal microtubules. Belongs to the CFAP20 family.