Component of the intraflagellar transport (IFT) complex B required for transport of proteins in the motile cilium (PubMed:28479320, PubMed:15916950). May be required for ciliary entrance and transport of specific ciliary cargo proteins such as che-3 which are related to motility (PubMed:28479320). Component of the IFT complex B composed of at least che-2, che-13, dyf-1, dyf-3, dyf-6, dyf-11, dyf-13, ift-20, ift-74, ift-81, ifta-2, osm-1, osm-5 and osm-6. Structural cilia defect: cilia are short and lack distal portions. Belongs to the IFT56 family.