Basically you take your old, unwanted polishes and trade them for discounted Zoyas! Last year, I ordered 10 polishes and mailed 10 of my old polishes to them. This year, I again ordered 10 polishes, but they are allowing us to donate our old polishes to worthy causes! I am donating my polishes to Hoosier Hills PACT, a local organization with a women's shelter. Most (if not all) of the polish I am donating is new and unopened - but if you choose to send your old polishes to Zoya, they don't have to be full or unopened. They can be old, crusty, thick or half empty bottles :)