Replacement rotor for Avid ball bearing disc brakes. Special manufacturing process resists warping and provides optimum braking. Avids unique design ensures the entire brake pad contacts the rotor, preventing uneven pad wear.. Choose 160mm for cross country, normal use, 185mm for more powerful braking for heavier and/or more aggresive riders, and 205mm for maximum braking more braking power on downhill bikes and other extreme uses.