Homophilic binding protein that enables kin discrimination in heterogeneous yeast populations by mediating homotypic cell-cell interactions during flocculation, a reversible and asexual process in which cells adhere to form aggregates (flocs). The Flo11 domain contains aromatic residues that form two hydrophobic bands on the surface of the protein that confer homophilic binding (PubMed:32286952). The hydrophobic bands are lined by stretches of acidic residues that may sensitise the protein to environmental pH (By similarity). Belongs to the flocculin family. Highly divergent.