What is the name of David Smith's most famous piece of artwork called?

David Smith's most famous piece of artwork is called "Cubi XX." Created in 1963, it is part of his series of Cubi sculptures, which are notable for their geometric forms and reflective surfaces. "Cubi XX" exemplifies Smith's innovative use of stainless steel and his exploration of abstract expressionism. The sculpture is celebrated for its dynamic interplay of light and form.