Zippers should close effortlessly , without resistance or snagging .

拉链的拉合应该毫不费力，没有阻滞感。

More than 7 billion zippers each year .

每年生产的拉链超过70亿条。

Something similar goes for light switches , zippers and even sex toys .

电灯开关、拉链，甚至成人玩具的情况也差不多。

And these zippers here need replacement .

还有这些拉链要换。

There are still tons of faulty zippers out there .

仍然有大量有缺陷的拉链存在。