Heidi Swapp-Lightbox Word Strips: Favorite. The perfect addition to the Heidi Swapp Battery Operated Lightbox (sold separately). Design custom signs for parties, evens and home decor! This package contains four 3x12-1/2 inch word strips in four designs. 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.