Shimano managed to add an additional cog in its Dura Ace 9000 11 speed cassette with a weight increase of only three grams vs. the Dura Ace 7900 10 speed cassette. Three grams. How'd they do it Two time tested yet innovative materials carbon fiber and titanium. You'll find titanium cogs for everything above a 16 tooth on this cassette, and you'll also find a carbon fiber carrier buried at the center of the cassette. And, while Shimano's not exactly known for an abundance of carbon in its designs, we don't doubt that it's just as finely engineered as its metals.