As a result of an inquiry you may be asked to send back specific information. This is a simple cover letter which tells the reader what you are sending them and why.
1234, Main Street
Boston, MA 02123
08 April, 2005
<Recipient Address Goes Here>
I have enclosed <what you are sending>.
<Optional desired action.> Please feel free to call me at <number> if you have any questions.
encl: <List of enclosed items goes here>