In the "Special Instructions" box put the name of the decal that you want to mirror.

If you have many decals in your cart please be very specific about the design name, quantity, and color you want mirrored.

This option is really only useful to those who want to put decals on the inside of the glass on their windows - facing outwards - This makes the text look correct from the outside.

Anyhow don't get too confused, you can see the mirror image preview on all designs by hovering over or clicking on the main photo displayed at the top of each product page. Try clicking the black white image on this page.