Free Spy Glasses

you can use these to see behind you. just save 2 glasses from a 3d movie

punch out the lenses and throw one of the frames away. now with the other frame pry the 2 pieces apart 

arange 2 lenses untill you have a dark purpleish color in the them.

put the doubled lenses in the bottom frame piece

glue the top frame on to the bottem one.  let it dry and put it on. it works best in a well lit room or outside. look to the sides of the lenses and you shold see behind you