And this is another 4" square card which is my favourite size. I find it's a good size for fitting a message inside without too much room left over - and isn't as hard to decorate as 3" square can be.
The only thing is it's a difficult size to find envelopes for so I have to make my own using the Crafter's Companion Enveloper Pro I bought a while back. This makes it easy to coordinate cards with envelopes (especially with something out of the ordinary like olive green!)
Size of card: 4" square
Card/paper - Cre8tive textured cardstock, Kaisercraft "Country Grove" patterned paper
Ink - Versacolor "Pinecone"
Stamp - Hero Arts sentiment
Tools - Fiskars paper trimmer, Carl corner rounder, Bostik glue tape, Fiskars "Clouds" paper edgers
Thanks for looking!