Étude Op. 10, No. 9, in F minor, is a technical study composed by Frédéric Chopin in 1829. This étude is part of the twelve studies which belong to Op. 10. It is widely regarded as a good left hand étude because it promotes flexibility in the wrists and fingers.
The above text from the Wikipedia article "Étude Op. 10, No. 9 (Chopin)" text is available under CC BY-SA 3.0.