Round 15mm is about 19/32" flat back acrylic (plastic) clear transparent cabochons. Height: 7.56mm. Light weight when compared to glass. Popular for jewelry making, DIY earrings, pendants, bracelets, etc. Simply have a print under it and let the magnifying effect do the job! Also used for acrylic displays as caps or feet, crafts and all kinds of decorations High Quality Professional grade, cabs are solvent bondable. Use your own glue Clear without any backing these cabs will magnify what is underneath.