Bearing Enduro Bearings ACB 4545 1125 Black Oxide 1-1/8"

ACB 4545 1125 BO – 1-1/8 Black Oxide angular-contact headset bearing (30.5mm x 41.8mm x 6.5mm: 45x45 deg).

Angular-contact headset bearing with anti-corrosion Black Oxide/Magnetite-coated 52100 high-carbon chromium alloy races and grade 10 balls. The Black Oxide coating provides an additional level of corrosion resistance and helps ensure extended, reliable performance.

This bearing size is also known in the bicycle industry by these part numbers:
MR042
870E
MR121
MR070
MR084
MR116
TH-870E
MH-P08

The Enduro line of angular-contact headset bearings starts with Black Oxide-treated chromium steel races and steps up to full 440C stainless steel. The Black Oxide headset bearings are treated in multiple chemical baths to achieve an anti-corrosive depth of 3 micron. This process also provides secondary heat treatment, making the races tougher. The BO races then undergo a secondary “super grind” to polish the rolling surface to a mirror finish. Both stainless steel and BO bearings are engineered to accommodate the largest possible balls, feature dual-lip seals riding in a micro-groove (labyrinth), and are filled 90% with extra high-pressure Almagard 3752 grease for protection against sweat and the elements. Enduro Angular Contact (A/C) bearings are designed so that all balls are evenly engaged, distributing force over a larger surface area to minimize wear and maximize bearing life.

Static load – 980lbf / 4.35kN
Weight – 19.24g