Shimano 105 CS 5800 11 Speed Cassette

Sure, new Shimano's CS 5800 has 11 nickel plated steel cogs to give you extra gearing options, but all the gears in the world aren't much good if you can't shift smoothly between them. Shimano optimized the ratios between each and every cog to provide smooth shifting and make sure that your cadence increases or decreases by equal amounts, regardless if you're shifting between the two biggest cogs or the two smallest. No jumps between gears means smooth, easy pedaling, which equals less fatigue and fewer losses of momentum, so those tough hills will float by a little bit easier than they used to.