The purpose of the tippet in tenkara fishing is to provide an extension of the main line and to attach the fly. The amount of tippet you use on a tenkara setup can vary depending on several factors, including your fishing conditions, the size of the fish you're targeting, and your personal preferences. Generally, tenkara anglers use a length of tippet between 3 to 5 feet (0.9 to 1.5 meters). Using a longer tippet allows for a more natural presentation of the fly and provides some additional distance between the fly and the main line, which can help prevent spooking fish in clear water.