This pack of 10 flat cotton wicks is made from 100 percent natural cotton fiber. Each wick measures 0.5 inches wide by 4.25 inches long (13 mm x 108 mm) and is designed to fit Eisco spirit lamps. The wicks provide proper capillary action for a bright, even-tempered flame. The natural cotton construction ensures clean burning suitable for laboratory heating applications. These replacement wicks extend the service life of spirit lamps used in chemistry and biology laboratories.