I've always liked to create thank you cards and invitations instead of buyng the boxed set. Of course, I get my thank you all ready to go - and where is the envelope! We've added envelopes to our mix for that very reason. A7 size is for a 5x7 card or foldover and the A2 size is for a 4 1/4x5 1/2 size. Our house is baby city and squeezing in the thank you's is....ahh you know what I mean!