Shimano might have been fashionably late to the 1x party but they made sure that upon arrival, the components had all gone through extensive engineering and real world riding so they were completely dialed and ready to up the trail game of the modern mountain rider. Shimano's FC-M9020-B1 XTR trail Crank Arms take everything we loved about the original M9020 Trail crank and added 3mm to the chainline so it would play nice with boost spaced (aka 148 OLD hubs) bikes. The propriety 96mm spaced, 4-bolt spider is designed for Shimano chainrings which feature a special tooth profile for maximum chain retention no matter how tough the trails get.Shimano strongly believes in using the right material for the right job and forgoes carbon fiber in crank arm construction and instead uses a 3D HollowTech II construction out of cold-forged aluminum for superior strength, durability, and light weight. The stainless steel teeth of the chainring designed for the single-ring Trail crank feature an alternating, semi-hook shape to aid in chain retention and the smoothness of the chain's engagement. Much like the arms, the rings too are hollow and add rigidity and shed weight. The trail crank's spider is the same found on all the M9000-series XTR cranksets, and so it can accommodate any M9000 single- or double-ring combination in the series.The Shimano FC-M9020-B1 Trail 1x Crank Arms come in a beautifully high-polished grey that will complement any top-end build. Lengths of 170 and 175mm are offered. The Q-factor is 174mm. The arms do not include chainrings or bottom brackets. Any and all chainring combinations that are compatible with these crank arms are designed for use with Shimano's 11-speed Dyna-Sys mountain drivetrains. Keep you boost bike all XTR with the FC-M9020-B1 crank arms.