Act your shoe size not your age.  Perfectly sound advice as it means that I can be 3 and a half!
( as an aside - the swing is actually created from a broken mud guard!)
blank inside for your own special message
A5 in size (14.8 x 21 cm,thats half the size of a standard piece of A4 paper)  these can be posted as a small letter.
Buy 5 for £12.99