When sourcing KYK bearings, you must prioritize dimensional accuracy and material composition. Ensure the bearings are made from High-Carbon Chromium Steel (GCr15), which is the industry standard for durability. Verify the ABEC rating (typically ABEC-1 to ABEC-5 for standard industrial applications) to ensure the precision level matches your machinery's requirements. Additionally, check the radial clearance (C2, C0, C3, C4); for high-speed or high-temperature environments, a C3 clearance is often necessary to allow for thermal expansion.