Abstract: Provided in the present invention are a leader for fly fishing comprising a monofilament of a vinylidene fluoride resin, said leader consisting of a butt section, a taper section and a tippet section, a diametral unevenness of the tippet section being less than 10%, and a process for producing such a leader for fly fishing. The leader for fly fishing according to the present invention has pliability to allow unrestricted movement of the fly and enough strength to withstand the impact of striking, and is also small in diametral unevenness and capable of having its curling disposition or kink easily straightened out.

Abstract: A detection method of a liquid level supplies fluid between a moving cylindrical body such as a parison in a film manufacturing process and an ultrasonic transmitter and receiver or an ultrasonic transmitter-receiver opposite to an outer surface of the cylindrical body to keep acoustic contact between an ultrasonic vibration member and the cylindrical body through the fluid. A level of liquid in the cylindrical body is measured on the basis of whether ultrasonic propagating in the fluid and the liquid in the cylindrical body can be received with a predetermined signal level or not. Since the ultrasonic vibration member is brought into contact with the cylindrical body through the fluid, and the contact state therebetween is kept good, and wear, flaw, deformation, frictional heat or the like is not given to the cylindrical body. Further, even if the surface of the cylindrical body is rugged, good contact can be kept.