There are several types of bending equipment and mechanics. The first one is compression bending, one of the earliest techniques of shaping pipes. It involves pressing a tube in a die with a preset shape, causing the tube to assume the form desired. Next is the rotary draw, that uses die sets with predetermined and unchangeable centerline radius, giving the tubes circular shapes. Roll benders have sets or rollers, that allow exercising pressure gradually, avoiding possible fractures and deformity.