Stereocilia (or stereovilli) are apical modifications of the cell, which are distinct from cilia and microvilli, but closely related to the latter.
Though their name is more similar to cilia, they are actually more closely related to microvilli, and some sources consider them to be a variant of microvilli rather than their own distinct type of structure. It is a long projection of cell membrane, similar in structure to microvillus
They are characterized by their length (distinguishing them from microvilli) and their lack of motility (distinguishing them from cilia). They contain actin filaments.