balletballet says:

An essential part of your ballet uniform. Pretty pink socks in a thin nylon to help you have good toes - not naughty toes!! 

Manufacturer says:

Simply ballet socks which are perfect choice for dance students
Great price and excellent quality!
The sizes in order of smallest to largest are:
1. Child 6 - 8.5 (US 6.5-9.5)
2. Child 9 -12 (US 9.5-13)
3. Child 12.5 - 3.5 (US 13-5.5)

Fabric: 88% nylon 12% elastane
Colour: Pink