Recommendation letter from previous employer

Hi There,

I have got to know from my consultancy that my status of the H1B petition is in RFE.

They are asking me to provide recommendation letter with detailed description of the project details from previous employers. This query is due to my education background (Mechanical engineer) different than IT or computer science. They are asking me to provide the information with company letter head.

My question is:

  1. If I don’t get the recommendation letter with letter head of the company.Will it be Okie to get the recommendation letter from my previous manager with business card?

  2. What else I have to take care?

Any help on this would be appriciated. Also share your ideas which I have to take along with this information.