Monofilament fishing line (shortened to just mono) is fishing line made from a single fiber of plastic material, as opposed to multifilament or braided fishing lines constructed from multiple strands of fibers. Most fishing lines are now nylon monofilament because they are cheap to produce and can be produced in a range of diameters which have different tensile strengths (called "tests" after the process of tensile testing, or possibly as a portmanteau of "tensile" and "strength"). Monofilament line is also manufactured in different colors, such as clear, white, green, blue, red, and fluorescent. Monofilament is made by melting and mixing polymers and then extruding the mixture through tiny holes, forming strands of line, which is then spun into spools of various thicknesses. The extrusion process controls not only the thickness of the line but its test as well. History DuPont made public in 1938 that their company had invented nylon. This new invention was the first synthetic fiber, fabrics that are commonly used in textiles today. In 1939, DuPont began marketing nylon monofilament fishing lines; however, braided Dacron lines remained the most used and popular fishing line for the next two decades, as early monofilament line was very stiff or "wiry", and difficult to handle and cast. Early monofilament did, however, have good knot strength and very low visibility to the fish, creating a small loyal following among fishermen. In 1959 DuPont introduced Stren, a thinner and much softer monofilament line that could be used in a large range of reels, including newly introduced spinning and spin casting tackle. Stren's monofilament lines soon became a favorite with many fishermen because of its overall ease of use and it spawned a whole host of imitators. New materials, e.g., Spectra or Dyneema, are finding growing usage as fishing lines. Polyvinylidene fluoride (also sold as fluorocarbon or PVDF) is very much like nylon monofilament, but has several advantages. Optical density is lower, which makes the line less easily discernible. The surface is harder so it is more resistant to sharp fish teeth and wear. Furthermore, PVDF does not take up water and it is resistant to UV-light. It is denser than nylon, too, which makes it sink faster. Dyneema is also becoming very popular and it is much stronger, but it is used mostly as a braided fishing line. Because the elastic stretching is only a fraction of that of nylon monofilament, the