The constructions of a pressure hull requires a high degree of precision. This is true irrespective of its size. Even a one-inch (25 mm) deviation from cross-sectional roundness results in over 30 percent decrease of hydrostatic load. Minor deviations are resisted by the stiffener rings, and the total pressure force of several million longitudinally-oriented tons must be distributed evenly over the hull by using a hull with a circular cross section. This design is the most resistant to compressive stress and without it no material could resist water pressure at submarine depths. A submarine hull requires expensive transversal construction, with stiffener rings located more frequently than the longitudinals. No hull parts may contain defects, and all welded joints are checked several times with different methods.