The Enduro ACB 6806 CC BO 1 3/8 BO Angular Headset Bearing (37 x 49 x 6.5mm; 36 x 45) is a high-performance 1-3/8" angular contact headset bearing, also known as HD446K, engineered for superior durability and smooth operation. It features anti-corrosion Black Oxide/Magnetite coated 52100 High-Carbon Chromium alloy races and grade 10 balls, providing enhanced corrosion resistance and extended worry-free performance. Designed with the largest possible balls, dual-lip seals riding in a micro-groove labyrinth, and filled 90% with high-pressure waterproof grease, this bearing offers ultimate protection against sweat and the elements. Its angular contact design ensures all balls are evenly engaged, spreading force over a larger surface area to minimize wear and maximize lifespan.