Just like in every industry, there is quite a lot of jargon used in apparel manufacturing and when it comes to socks, people often refer to tube socks when talking about knee-high models but there is big difference between these two models.
First, while a knee-highs go by definition as high as the knee, tube socks can be longer or smaller. More importantly, knee-high socks are regular socks. However, the biggest difference between these two models is that a tube sock doesn’t include the foot, which is why it is called tube.
So for all you looking into making socks for sports or as part as an apparel line, make sure to ask for knee-high socks, not for tube!