The first USB charging cable fast charge and slow charge the difference is that the size of the wire diameter is not the same, the fast charge wire diameter must be thicker, slow charge wire diameter can be thinner. Fast charging wire is suitable for fast charging and slow charging, slow charging wire can only be used for slow charging.
The second USB charging line fast charge and slow charge for the charging line to withstand the current size is not the same, fast charge line can withstand large current.