That is the size of a standard sports trading card. The rule about size is the ONLY rule in the ACEO world. An ACEO
can be created in any medium the artist desires: paint, colored pencils, ink, etc. There are even ACEOs made from wood,
clay, fabric, and metal.
ACEOs are tiny art works that can be matted and framed to hang on the wall. Many people display
their ACEO collections in the same kind of plastic sheets and albums that sports card collectors use.
You might slip an ACEO into a greeting card as an extra surprise for a birthday, anniversary, or Christmas. Available here starting at .99 cents