45 Flat Back Rhinestone Mixed Valentine Assortment Gems. These are great for ATCs and other art projects. There are 10 facet rhinestone flat back gems that measure 6mm in diameter 5 red and 5 pink, 10 flat back pink iridescent pearl gems that measure 6 mm in diameter, 5 flatback red pearl gems that measure 6 mm in diameter, 10 flat back red iridescent pearl gems that measure 8 mm in diameter and 10 flat back white iridescent pearl gems that also measure 8 mm in diameter. Just use tweezers or our Bead, Pearl & Rhinestone Wax Picker Pencil Tool to add a little glue to the back and then position and adhere to artwork.