These are the stickers that took off in the mid '70s to become a huge seller for Topps. Since most of the stickers were used by kids for their original purpose (sticking them on things), most of them did not survive. They aren't very sturdy either, so many of them that have survived are not in great condition. A complete set of all 16 series in nice shape currently sells for around $1000. The middle series (5-9) are most common. The early series (1-4) are harder to find in nice condition, and the later series are in shorter supply. Many collectors I've had contact with never saw any of the last 2 series in stores and had to buy them from dealers (including me). A lot of stores must have stopped carrying them as their popularity waned.