Trek ZS56/ZS66 Headset Bearing Kit MH-P03K Material: 100CR6 Chrome Steel

Material: 100CR6 Chrome Steel

Suits both Carbon and Alloy frame bikes

if you’re still not sure

4 Different Part ref's)

Upper Bearing - AC3544

Trek ZS56/ZS66 Headset Bearing Kit MH-P03K Material: 100CR6 Chrome SteelBoth the upper and lower headset bearings, two bearings included in sale. For all Trek bikes using the ZS56 ZS66 Headset Bearing Kit GCR15 High Carbon Chromium Bearings: Chromium offers a corrosion resistance to the bearing, allowing you to get more use out on the trails and less time in the workshop changing bearings again due to rust and seizing. Buna NitrileRust Resistance Seals: Prevents moisture getting inside the bearing. Packed With Lithium