This flat bearing washer provides the axial support surface required for needle roller and cage thrust assemblies, taking up axial load while allowing the needle rollers to run directly against a hardened, ground raceway. Symbol LS5578 has a width of 5.0 mm and a net mass of 88.2 g, matching the dimensional series used with AXK and K811 thrust assemblies. Because it carries no separate rolling elements or cage, this washer must always be paired with a corresponding AXK or K811 needle roller and cage thrust assembly to form a complete thrust bearing. The flat, ground contact face keeps axial clearance low and allows precise positioning within a housing, while lubrication (grease or oil) is applied according to the mating assembly's requirements rather than to the washer itself.