A Boxing bag (or, British English, punchbag) is a sturdy bag designed to be repeatedly punched. A punching bag is usually cylindrical, and filled with various materials of corresponding hardness.
Punching bags are often filled with grains, sand, rags, or other material, and are usually hung from the ceiling or affixed to a stand. Other bags have an internal bladder to allow them to be filled with air or water. The design of a punching bag allows it to take repeated and constant physical abuse without breaking. The bag must also absorb the impact of blows without causing harm to the user.