Upper and lower bearing kit in 440C stainless steel for Trek Madone frames 2019 and later. Replaces Trek bearing numbers W513538 and W540243

440C stainless steel balls and races provide long life and superior corrosion resistance in applications and environments that may be less than ideal. 440C has the highest strength, hardness, and wear resistance of all the standard 440-series stainless alloys with high carbon content.