All superlines are made of polyethylene, a chemically inert, slippery plastic. The plastic is spun into extremely fine filaments that are in turn combined into a thread. The threads are usually then braided into fishing line of assorted thicknesses and strengths. Common to all such lines are extreme sensitivity, low stretch, and very high strength in proportion to line diameter. Retail prices are higher than for nylon monofilaments, partly because the manufacturing process is relatively complex.