Coir fibers are found between the husk and the outer shell of a coconut. The individual fiber cells are narrow and hollow, with thick walls made of cellulose. They are pale when immature but later become hardened and yellowed as a layer of lignin is deposited on their walls. Coir is used in floor mats and doormats, brushes, mattresses, floor tiles and sacking. A small amount is also made into twine.