Self-aligning ball bearings consist of two parallel rows of balls, a common sphere shaped raceway located in the outer ring and two deeper raceway grooves in the inner ring. The bearings are impervious to angular misalignment of the shaft when deflecting. SKF self aligning bearing come in either open type or rubber sealed. 

Self aligning Bearings with the suffix K in their title are taper bored, because of this they will require an adapter sleeve, an example of this 2320KMC3 as you can see the K has been made bold for demonstration purposes. The adaptor sleeves are available in both metric and imperial bore sizes.