From the manufacturer:
These lightboxes feature dimmable LEDs that provide an even spread of light from edge-to-edge. They are ultra slim at .31" thick and light-weight. The lightboxes include a built-in ruler grid and are ideal for tracing, calligraphy, stenciling, embossing, quilting, embroidery, sewing and more. They are powered by an AC adapter and produce very low heat. Cable measures 71"