You could keep browsing for the perfect greeting card... But you're already here so you might as well just settle on this one. It'll do, right?
 
Details:

Size: A6 (105 x 148mm / 4.1 x 5.8 inches).
Printed on FSC Board - this means that the paper is produced from sustainable forests and/or recycled materials.
Blank inside for your own message.
100% recycled brown Kraft envelope supplied.
Made in the UK.