A sponge made from cellulose, a cellulose material extracted from wood waste. Before use, it is a card about 2 mm thick, but when wetted with water, it expands to about 2 cm and becomes a soft sponge. It absorbs plenty of water, creates a good lather for detergent, and drains water well. It is a slim card type that does not take up much space, so it is convenient to store it.