Same hard drives, different capacities

I have two exactly same hard drives WD Reds 6TB, but they have slightly different capacities, is this normal or there are some bad sectors or something like that on them?

The discrepancy appears to be caused by partition table differences.

• Although the physical disk capacities are identical, the capacities listed in Disk Management are different. This would mean that the disks were initialized differently. Disk Management reports the capacity as indicated by the partition table, not the physical capacity of the disk, and may report the wrong capacity if the partition table specified a disk size other than the real capacity of the media.

• This oddity is likely to be due to the drives having been first initialized on two different operating systems. Reinitializing both drives on the same system (which would erase all data on the drives) would equalize their capacities. To do this on Windows, use the clean command in DiskPart on an elevated command prompt to wipe the partition table, then use Disk Management to initialize the partition table again.