Guanine nucleotide exchange factor for Rab GTPase Rab-11.1 (By similarity). May spatially and temporally regulate the distribution of Rab-11.1 to target membranes during embryogenesis (PubMed:26506309). May play a role in cytokinesis, probably by targeting rab-11.1 to the cleavage furrows (PubMed:26506309). Interacts with rab-11.1. Binds preferentially to the GDP-bound form of rab-11.1. Expressed during embryogenesis. Viable. Double knockout with rei-1 results in a smaller brood size, weak embryonic lethality and severe mislocalization of rab-11.1 and prolonged cytokinesis in embryos. Belongs to the SH3BP5 family.