Heidi Swapp-Lightbox Inserts: Alphabet. The perfect addition to the Heidi Swapp Battery Operated Lightbox (sold separately). This package contains fifty 3x1-1/2 inch lightbox inserts. Comes in a variety of colors. Each sold separately. WARNING: This product contains chemicals known to the State of California to cause cancer, birth defects or other reproductive harm. Do not mouth or chew. Imported.