Which of the following is a standard size for metric fasteners?

The standard size for metric fasteners is determined by the screw diameter and the thread pitch, both of which are crucial for ensuring compatibility with corresponding components. The notation used for metric fasteners generally consists of an "M," followed by the diameter in millimeters and the thread pitch in millimeters.

In this case, M8x1 denotes a fastener with a nominal diameter of 8mm and a thread pitch of 1mm, which is a recognized standard in the metric system. The first part, "M8," ensures that the fastener is correctly sized for applications requiring that specific diameter, while the thread pitch of "1" specifies how tightly the threads are wound around the shaft.

This understanding helps in identifying that other options may represent valid metric fastener sizes as well; they simply relate to different diameters and pitches. M6x1 refers to a different diameter and pitch, M10x1.5 indicates a larger diameter with a specific pitch, and M12x1.25 reflects an even larger size. However, the choice of M8x1 is particularly noted for being a prevalent standard in various applications across the industry.