consist of a tough braided or monofilament core, wrapped in a thick waterproof plastic sheath, often of polyvinyl chloride (PVC). In the case of floating fly lines, the PVC sheath is usually embedded with many 'microballoons' or air bubbles, and may also be impregnated with silicone or other lubricants to give buoyancy and reduce wear. In order to fill up the reel spool and ensure an adequate reserve in case of a run by a powerful fish, fly lines are usually attached to a secondary line at the butt section, called backing. Fly line backing is usually composed of braided dacron or gelspun monofilaments. All fly lines are equipped with a leader of monofilament or fluorocarbon fishing line, usually (but not always) tapered in diameter, and referred to by the 'X-size' (0X, 2X, 4X, etc.) of its final tip section, or tippet. Tippet size is usually between 0X and 8X, where 0X is the thickest diameter and 8X is the thinnest. There are exceptions to this, and tippet sizes do exist outside of the 0X-8X parameter. Tenkara lines are special lines used for the fixed-line fishing method of tenkara. Traditionally these are furled lines the same length as the tenkara rod. Although original to Japan, these lines are similar to the British tradition of furled leader. They consist of several strands being twisted together in decreasing numbers toward the tip of the line, thus creating a taper that allows the line to cast the fly. It serves the same purpose as the fly-line, to propel a fly forward. They may be tied of various materials, but most commonly are made of monofilament. Wire lines are frequently used as leaders to prevent the fishing line from being severed by toothy fish. Usually braided from several metal strands, wire lines may be made of stainless steel, titanium, or a combination of metal alloys coated with plastic. Stainless steel line leaders provide: - bite protection - it is extremely hard for fish to cut the steel wire, regardless of jaw and teeth strength and sharpness, - abrasion resistance - sharp rocks and objects can damage other lines, while steel wire can cut through most of the materials, - single wire (single strand) leaders are not as flexible as multi strand steel wire, but are extremely strong and tough, - multi strand steel wire leaders are very flexible, but are somewhat more abrasive and