This steel rear axle provides maximum durability for E-sync and Neo 12x148mm Boost hubs. Weighing only 40g more than an alloy axle, the steel axle provides a significant increase in durability. This axle features a high-precision centerless ground treatment that ensures perfect bearing fit. Compatible with E-sync and Neo 6-bolt and Centerlock hubs. Not compatible with 135mm, 142mm, 150mm, 157mm, or single-speed E-sync and Neo hubs. Not compatible with M-pulse hubs.