Backflow Incense Cones when they are burned, the smoke flows down the incense tower like a waterfall, creating an unusual and beautiful effect. These cones are only for use with Backflow Incense Burners. Each box contains 10 cones Warning: Keep away from children. Backflow Incense can damage varnished surfaces, always use on a mat. To be used indoor and with no drafts for best effects.