Nylon coated beading wire. Use crimps to secure. 20 lb test strength. Best for very large beads, lampwork, silver, ethnic, chunky, heavy beads or beads with large holes. By the 30 ft spool. 0.609 mm diameter, 9.144 m length. 19 strand. Free of heavy metals. Recyclable. Non-tarnish. Extreme Abrasion resistance. Even the spool is recyclable. Nice enough to let it show.