Is individual client letter mandatory for H1B stamping for new client?

[watashiwaarun]

Hi,

I quickly need a clarification on H1B stamping mandatory documents. I have a valid H1 petition for a different client while stamping is being done for the new client. Is an individual client letter needed for stamping or a generic client letter alongwith SOW/MSA documents?

Preferably if anyone had received stamping recently can provide clarifications on this issue.

Regards,
Arun