The Penguin Feet rack pads are easily the coolest and highest quality rack pads on the market. The Round Feet pads are built to fit around round or square cross bars.  Look at the Flat Feet rack pads if you have aero style cross bars.  Here are the details:

• 30" - some of the widest rack pads on the market.
• Long Lasting closed cell foam that won't disintegrate over time.
• Durable Neoprene cover that is soft to the touch and easy on your gear.
• Velcro closure from end to end to keep your Round Feet securely on the crossbar.
• Mesh bag with loop closure to store your rack pads when not in use