Component of the ESCRT-II complex (endosomal sorting complex required for transport II), which is required for multivesicular body (MVB) formation and sorting of endosomal cargo proteins into MVBs. The MVB pathway mediates delivery of transmembrane proteins into the lumen of the lysosome for degradation (By similarity). Component of the endosomal sorting complex required for transport II (ESCRT-II). Belongs to the VPS25 family.