FireLine is a pre-waxed, braided cord consisting of gel-spun polyethylene, which is known as the strongest fiber, per diameter, ever created. It has an unbelievably high tensile strength and has been recommended in numerous how-to articles on beadworking. The 4 & 6 lb. tests will fit a #12 English beading needle. We highly recommend the Xuron 441 cutters for cutting FireLine.