>120 deniers This is used during the coldest temperatures in midwinter.　 Completely opaque; the leg looks thicker because the tights need to have some layers on its surface. It's so warm... For some reason, it's surprisingly not sweaty.

With my own personal opinions.

For the Gentleman: A Rough Explanation on the Denier Unit for Pantyhose and Tights. Denier is a measurement for the linear mass density of fibers.

>40 deniers Worn during the start of Spring, Autumn, etc. Its sense of transparency is totally subtle. The thighs and the rest of the leg are quite visible too. It's erotic. The wearer's legs are barely being shown.

>80 deniers This is for winter, it's typically thick. It's also nearly opaque. Some skin colour can be faintly seen, so I'm happy when I find it. Wearing it with boots makes it too sweaty.

These are garter stockings.

>20 deniers For Spring-Summer use. See-through. I can't think of anything else but choosing and wearing one of these.