Joel Drucker discusses the green clay and Caroline Wozniacki in "Angles and Drop Shots from the Volvo Car Open" READ: http://tennischannel.com/reporters/joel-drucker/joel-drucker-angles-drop-shots-from-the-volvo-car-open

50 Shades of ClayThe clay surface at the Volvo Car Open is called “green clay.” Prevalent in the United States, green clay is the informal name of a surface called Har-Tru. Many players prefer the green because it is faster than the red clay of Europe.