Chalkboard erasers are typically made of felt, which is a non-woven textile material. The felt is attached to a wooden or plastic handle. Some erasers may also have a magnetic strip on the back, which allows them to be attached to a chalkboard.
Felt is an ideal material for erasers because it is soft and absorbent, and it does not damage the chalkboard surface. It is also relatively inexpensive and easy to manufacture.