balletballet says:

These leggings will add shine to any performance.  A great basic to go with any leotard. Elasticated waist and footless bottoms.  

Manufacturer says:

Popular choice of footless dance tights for children & adults!
Made from a silky, shiny Nylon Lycra which looks great, feels great and is highly durable
Great to team with matching nylon lycra garments.
Fabric: 80% Nylon/ 20% Elastane
Colours: Black