Enables GTPase activator activity. Acts upstream of or within several processes, including Ral protein signal transduction; activation of GTPase activity; and regulation of exocyst localization. Predicted to be located in cytosol. Is expressed in central nervous system and retina. Orthologous to human RALGAPB (Ral GTPase activating protein non-catalytic subunit beta). [provided by Alliance of Genome Resources, Apr 2022]