DIN
DIN stands for Deutsches Institut für Normung and is Germany's national standards organization (German Institute for Standardization). It is also the German member body for the ISO.
DIN has its own standards for bearing tolerances (P2,P4,P5,P6,P0). For skateboard bearings, DIN uses DIN 625-1 "Rolling bearings; single row radial contact ball bearings" instead of the ABEC or ISO ratings.
See ABEC Rating