The revolutionary Twinwall handlebar is an oversized diameter 1-1/8 inch (28.6mm) handlebar which utilizes two tubes, one within the other, borrowing principles from aircraft design to give the best combination of lightness, strength and safety. Since their introduction in 1998, the Twinwall has been the handlebar of choice for more professional race teams and has helped more riders win championships than any other handlebar in the world. Fits model: Windham.