The Polaroid Step Up Or Step Down Adapter Rings are a reliable and economical way to use filters and conversion lenses. They allow you to use smaller size filters or conversion lenses on lenses or cameras with a larger diameter thread or vice versa it allows you to use a bigger size filter or conversion lens on a lens or camera with a smaller diameter thread . The first number is the size that screws into the lens and the second number is the filter size/mounting thread size.