Ceramic bearings reduce drag in your hubs, and they do it in a dramatic way in comparison to the machine-quality cartridge bearings that come stock in most wheelsets -- even high end models. Ceramic bearings are measurably-and-devilishly round, and it's this roundness that gives them their rolling slickness. The reduction in mechanical drag you get by upgrading to ceramic bearings is no different than magically shedding ounces off your bike on a climb. For a given wattage, your speed increases. Period. According to tests the use of their ceramic bearings (including the specially formulated lubricant they roll in) gives you an added 20m-40m per 1km ridden. And keep in mind that mechanical drag is utterly unlike aerodynamics -- it becomes more and more critical the lower your speed is. According to these tests, the use of ceramic bearings decreases friction 22-fold. It's not personal, it's just physics.

Enduro offers a ceramic bearing upgrade kit for Mavic Crossmax SL and SLR wheels. You'll get a total of 5 bearings in 3 sizes -- 2 for the front wheel, 2 for the freehub body, and 1 for the non-driveside of your rear hub.