Heidi Swapp Lightbox Alphabet Inserts - White Bold on Clear The perfect addition to the Heidi Swapp Battery Operated Lightbox (sold separately). This 3 1/2 x 3 3/8 x 1 1/4 inch package contains fifty lightbox inserts. 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.