Clear monofilament or fluorocarbon leader weighing 40 to 50 lb. The higher weight leader line acts as a shock absorber during vigorous strikes and provides increased abrasion resistance for a catfish's rough mouth. Simply match the swivel size to the size of catfish you intend to catch. A leader is a piece of fishing line that attaches a hook to a bait or lure. Leaders are used when trying to catch fish that are not easy to catch with a hook and line alone, such as large game fish or sharks. Fish feel secure while feeding on a bait or lure, so they are less likely to bite off their own head if it tries to eat something nasty. However, if you do want to catch some very dangerous fish, then a leader is necessary for your safety as well as theirs. There are several different types of leaders, depending on what type of fish you are trying to catch. Flourocarbon leaders are the most durable because they are made from polyethylene terephthalate (PET) material. They will also stand up to high temperatures like those found in an oil spill. Clear monofilament leaders are next in line after fluorocarbon leaders. They are used primarily for freshwater fishing because they are more flexible than their saltwater counterparts. Saltwater anglers should use nylon leaders because these leaders can withstand the corrosive effects of sea water.