Toshiba MQ01ABD100 - Which parameters match for head swap?

[SOSdonnees]

Hi,

Given two 2.5'' Toshiba drives of the same model (MQ01ABD100), which parameters should be matched for heads replacement?
(Drive revision ?, Country ?, Date ?)

I read that the DRIVE REV is the firmware, but I assume that the firmware version could be only some digits of the DRIVE REV.<
For instance, what is the difference between a :
AZA AA00/AX001U
and a
AZA AA00/AX001A

Thanks.