Sram Cassette Xg 1251 D1 Silver 12 Speed Xplr GearingFeatures X Range technology provides a wider range and smoother gear changes so you can get the right gear every time. 440% range provide the coverage desired by 1x Gravel riders. For use with XPLR 1x rear derailleurs. Compatible with Flattop chains Fits XDR freewheel bodies Specifications Speed 12 Speed Combination(10 44T): 10 11 13 15 17 19 21 24 28 32 38 44