Stimulates guanine exchange activity of SOS1. May play a role in membrane ruffling and remodeling of the actin cytoskeleton (By similarity). In the cochlea, is required for stereocilia maintenance in adult hair cells (By similarity). Interacts with ABI1. Part of a complex that contains SOS1, ABI1 and EPS8L2. Associates with F-actin (By similarity). Localizes at the tips of the stereocilia of the inner and outer hair cells. Belongs to the EPS8 family.