Baker's dozen mix of lenses, mirrors, prisms, and/or strange optical things that we have only small quantities of. No two grab bags are the same. Many of the items you receive are each worth much more than our $10 price for the grab bag. You'll be pleased or your money back, no questions asked. You may get some optical stuff that we don't have a clue what it is used for. Your opportunity to get creative with this stuff and have fun.