Cilium- and flagellum-specific protein that plays a role in axonemal structure organization and motility (PubMed:34715025). Involved in the regulation of the size and morphology of cilia. Required for axonemal microtubules polyglutamylation (By similarity). Microtubule inner protein (MIP) part of the dynein-decorated doublet microtubules (DMTs) in cilia axoneme. Expressed in trachea multiciliated cells. Expressed at high levels in germinal vesicle stage oocytes at the mRNA level. Expression peaks in 2-cell embryos and decreases thereafter. Hardly detectable in morula stage embryos. This pattern of expression suggests a maternally derived transcript. Belongs to the CFAP20 family.