Exalith, a treatment given to Mavic's upper-echelon of wheels, penetrates the rim's alloy in order to delay rim wear and to enhance braking power. It's also a key component in maintaining the rim's distinctive Anthracite Grey color. However, you need to use the Mavic Exalith II Brake Pads in order to enjoy these benefits. These Mavic brake pads are specifically designed to work with Mavic's Cosmic Carbone SLR, Cosmic Carbone SLE, R-Sys SLR, and Ksyrium SLR rims. In order to prevent premature wear of the rim, Mavic recommends only using these Exalith II Exalith II Brake Pads. Please note that these pads are sold as a pair.