Precision component group used for positioning, rotation prevention, and power transmission of mechanical parts. Includes dowel pins, knock pins, taper pins, spring pins, parallel keys, square keys, serration keys, etc. Essential components for shaft-hub coupling, part positioning and fixing, and rotational torque transmission. Mainly JIS standard products made from carbon steel such as S45C and stainless steel like SUS304. Frequently used in assembly and maintenance of NC machining centers, machine tools, industrial robots, and conveying equipment. Unlike screws and bolts, primarily provides fixing function through fitting.