Soft enamel challenge coins are the most popular coin choice. Recessed metal are infilled with bright and colorful soft enamels. The enamels are lower than the raised metal rim. Epoxy are avaiable to cover the surface to make it more smooth and durable. The metal bases are available in gold, silver, copper, dye black, and could be anqitued or sandblasted. Various kinds of attachments including acrylic box or PVC bags are available.