You have been browsing for hosiery, etc. pantyhose, stockings. I'm sure you are wondering what does all those number with a D that follows meant.
Well the D stands for denier, which is the unit of measure for thickness of hosiery fiber, the higher the number the thicker the hosiery gets.
Starting from the lower 10-20 denier Hosiery is light and sheer, which is suitable during spring / summer season.
21 to 50 denier are slightly thicker but still sheer, and are suitable for spring / fall season.
50 denier & more are thicker and are suitable for winter.
Hopefully this clear some confusion as to what those numbers meant.