Jan, you're an Aussie like me and this got me too when I started, lol. A2 is the standard US card which is ever so slightly fatter and shorter than our A5 folded in half card. So the measurements are around 14cm x 11cm (that's a rough measurement. I'm too lazy to look it up).
And for the US ladies, our A2 card is much, much bigger than yours so that's where some confusion can creep in in tutorials.