求翻译：The inner peripheral surface of the opening 16 made in the flange 6 of the base 2 includes two diametrically opposite planar surfaces 16a forming flat sections extended on either side by the opposite circular surfaces 16b of the opening, thereby giving the opening 16 an oblong shape matching the oblong shape of the tub是什么意思？

待解决 悬赏分：1 - 离问题结束还有