The strength and functionality of rods have been improved in line with the evolution of materials, from bamboo, to glass fiber, to polyester resin. In the latter half of the 1970s, carbon fiber, which was a more lightweight and stronger material, came into popular use. Shimano also focused on the development of products using carbon fiber. In 1978, it released the Hihou carbon rod. The conventionally mainstream manufacturing method, which used both carbon fiber and glass fiber, was replaced by a combination of carbon fiber and Kevlar fiber using a proprietary structure to overcome the problem of easy breakage. A skinny design was employed to allow anglers to feel lightness and flexibility in casting as well as durability. These features fascinated experienced anglers. Hihou boosted the profile of Shimano’s carbon rods. The Hihou series was deployed in various fishing categories until the X structure was developed in 1981.