Is/are a contractile ring of actin microfilaments that eventually results in the division of the cytoplasm.

CONTRACTILE RINGS are a contractile ring of actin micro filaments that eventually results in the division of the cytoplasm.
The contractile ring are usually formed during the early anaphase phase of the cell division cycle. During the cellular cleavage, the contractile rings tighten around the cytoplasm of the cell until it is pinched into two daughter cells.