Moving Announcement Postcard - We've Moved Cards - Change of Address - Blank 4x6 Inch Post Cards - Pack of 25 Set of 25 Moving Announcement Postcards We've Moved Cards can be mailed with Postcard Stamps to recipients. Card size 4" x 6" inches made from heavy matte cardstock, Double Sided Back is pre-printed with postcard layout. Handwrite, label or stamp your new address on the blank cards.