Made of vinyl, they have the sticky part on the back of the sticker.
The vinyls and inks are weatherproof making them hardwearing for outdoor and indoor usage. Surface stickers can have any colour background or be clear (clear transparent stickers need to be stuck on a light coloured surface for the print to be seen clearly).
Once surface stickers are removed they cannot be re-used. The vinyl has a life expectancy of 3-5 years outdoors.