Heidi Swapp Lightbox Inserts Party. Complementary icon sets are the perfect addition to your Lightbox collection. Customize your sign with icons for a fun, trendy look. This 3 1/2 x 3 x 1/2 inch package contains twenty unique 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.