30.6 cm x 19.4 cm
From the Winthrop family papers.
The item is comprised of a large sheet of paper that was folded in half, and then folded again. Bradford wrote his letter (page 1) on one half of the paper. On the other half, Bradford wrote the address (on the top of page 2) and John Winthrop wrote notes about his response to the letter (on the bottom of page 2).