Component of the IFT complex B required for sonic hedgehog/SHH signaling. May mediate transport of SHH components: required for the export of SMO and PTCH1 receptors out of the cilium and the accumulation of GLI2 at the ciliary tip in response to activation of the SHH pathway, suggesting it is involved in the dynamic transport of SHH signaling molecules within the cilium. Not required for ciliary assembly. Its role in intraflagellar transport is mainly seen in tissues rich in ciliated cells such as kidney and testis. Essential for male fertility, spermiogenesis and sperm flagella formation. Plays a role in the early development of the kidney. May be involved in the regulation of ureteric bud initiation (By similarity). Component of the IFT complex B, at least composed of IFT20, IFT22, HSPB11/IFT25, IFT27, IFT46, IFT52, TRAF3IP1/IFT54, IFT57, IFT74, IFT80, IFT81, and IFT88. Interacts with IFT27. Interacts with IFT88 (By similarity). Detected in placenta. Belongs to the IFT25 family. Was initially classified as a member of the small heat shock family protein. However, it was later shown that it is not the case (PubMed:19921466).