With clear acrylic housings you can visually check that the 'o' ring is seated correctly in the groove by looking through the side of the housing BEFORE entering the water.
现在的树脂外壳，可以让你非常方便在下水前观察O型圈是否就位妥当。
2
The sealing ring cross section is V-shaped, and inner groove between two side edges composed the V-shaped is formed by tangency of two arcs with different radiuses.
密封圈的横截面呈＂V＂字形，构成＂V＂字形的两个侧边条之间的内槽由两个半径不等的圆弧相切而成。
3
The inner side of the rubber ring glasses frame is provided with a groove which is used for fixing the shortsighted lenses.