Original equipment on SRAM and Truvativ cranks, they also work well with other drive trains. Original replacement rings for Sram X.9/X.0 2 x 10 Systems Outer rings are ramped and pinned X-Glide Specific: Use 26t inner with 39t outer 4 Bolt pattern: 80mm Inner/120mm outer BCD 7075-T6 aluminum construction with a blast-black anodized finish treatment and CNC/laser detailing for 10-speed drivetrains (X.0 level)