Responsive Icons. Does that ring a bell?
Anyway, this icon set contains 10 icon concepts that are designed in 3 different sizes (Small, Medium and Large), optimized with various amount of details. Moreover, it comes with 3 variations of styles as well: Line, Solid and Flat style. That’s basically 120 icons!
If you like what you get, don’t forget to check out the rest icons from this series at this public collection: http://graphicriver.net/collections/4666418-responsive-icons/