7021A

The thickness of the outer ring is different for the marked and unmarked sides of angular contact ball bearings. This is due to the contact angle between the outer ring and balls. Conversely, the thickness of the outer ring in deep groove ball bearings is equal on both sides.
Additionally, ACBBs have 7xxx designations, while DGBBs have 6xxx designations.

Double-row ACBBs can take axial loads in both directions, but they have limited contact angle options.
ACBB arrangements or multiple single-row ACBBs can only take axial load in one direction based on how they are combined. However, multiple-bearing options have no limits for contact angle, allowing for a custom selection to best match the ratio of radial load to axial load.
Additionally, the clearance and precision of ACBB arrangements is controlled as a set, creating a stable level of vibration/noise and rotational accuracy. However, using two single-row ACBBs that are controlled individually can cause significant variation in their resulting properties when combined.

As their name implies, the balls and outer ring in an ACBB make contact diagonally at the specifed contact angle. The contact angle affects the inclined contact made between the balls and outer ring, thereby affecting limiting speed and load capacity. The larger the contact angle, the higher the bearing's axial load capacity.