H1B Transfer : From Company A to B (in India) - Client Letter

Hello, I had H1B from Company-A and worked in US from 2013 to 2015 and came back India (Petition Got expired on Dec 2016). Now I am working with Company-B - joined Dec 2016. Question is :- Since My case fall under Cap Exempt and Company B is doing H1B Transfer, Should I provide Client Letter at the time of stamping/Filing?
would Manager letter be enough? I am providing all other relevant document.

It depends on how your petition was filed. Yes, in general, Client Letter is good document to carry…if not, need to carry supporting documentation like MSA, SOW, etc. Carry as much documentation as you can…