ACB 3645 CC BO 1-1/8" Angular Contact Black Oxide treated Headset bearing (30.2mm x 41mm x 6.5mm: 36x45 deg) -

Black Oxide

Angular-contact headset bearing featuring anti-corrosion Black Oxide/Magnetite coated 52100 High-Carbon Chromium alloy races paired with grade 10 Balls. Black Oxide coating provides an extra level of corrosion resistance and extended worry-free performance

XD-15

Internal headset bearing featuring XD-15 races and balls to provide a lifetime corrosion resistance

The last headset bearing you will ever install into your bike.
These full XD-15 bearings are virtually identical in performance and torrosion resistance to our XD-15 Ceramic-hybrid bearings used for hubs and bottom brackets, but with XD15 balls that work better in the more abusive steering environment. The mechanical properties of XD-15 stainless steel balls provide a level of impact resistance superior to ceramic balls for headset application. Enduro testing of bearings with XD-15 balls and races have been run salt water for months without any corrosion, there is simply nothing on the market that compares. We are so confident in this material that we guarantee these full XD-15 headset bearings for life, against corrosion.

This size bearing is also known in the bike Industry by these part numbers:
27287-1046-004
HSS0130K
TH-873E
MR-122

The Enduro line of angular-contact headset bearings start with Black Oxide treated Chromium steel races, steps up to full 440C stainless steel, and the top of the lines, lifetime-guaranteed, XD-15 aerospace-stainless (races and balls). They are always engineered with the largest balls possible, feature dual-lip seals riding in a micro-groove (labyrinth) and are filled 90% with high pressure water proof grease for the ultimate protection against sweat and the elements. Enduro Angular Contact (A/C) bearings are designed so all balls are evenly engaged to spread the force over a larger surface area, decreasing friction, minimizing wear and maximizing life.

Static load - 935lbf / 4.15kN
Weight - 19.24g