For a coating to perform properly during use, the paint must have the proper amount of flexibility to withstand cracking under stress. A common test is bending a coated panel over a cylindrical or conical shaped bar. A mandrel bender is commonly used to test for paint flexibility. A cupping tester is another coating flexibility tester that slowly pushes a round punch through a coated panel until cracking occurs in the paint film. The degree of bending or deformation of the coated surface is measured to assess the coating flexibility.