ACB Mini 276442 SS - 1 440C Stainless Steel Angular Contact Headset Bearing (14.2mm x 25mm x 6.5mm: 45 x 45deg) -

Angular-contact headset bearing featuring 440C stainless steel balls and races for superior corrosion protection.

This size bearing is also known in the bike industry by these part numbers:
307481
W 276442

Not all stainless steel is created equal.

The Enduro line of angular-contact headset bearings starts with Black Oxide treated Chromium Steel races and then steps up to full 440C stainless steel. 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 waterproof 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, minimizing wear and maximizing life.

Static load - 320 lbf, 1.42 kN
Weight - 8g