Array of options delivers optimal gravel gearing for variety of needsThe SHIMANO FC-RX610-1 crank balances weight savings, optimized efficiency and an array of gearing options that cater to the segmented demands of mixed-terrain riding. By pairing a 10-45T or 10-51T cassette with 38T or 40T chainring, riders can choose closer gear steps or ultimate range depending on personal need. The FC-RX610-1 comes in 165, 170, 172. 5, and 175 mm crank arm lengths, providing an additional level of customization.