Which sizing is used for a 5/8" guy rod?

The appropriate sizing for a 5/8" guy rod is 12M. The "M" designation typically refers to the metric size that corresponds to the diameter of the guy rod in millimeters.

In this case, a 5/8" diameter rod is approximately 15.88 mm when converted from inches to metric. The closest size available in standard sizing increments for a guy rod would be 12M, which is often used in communications and cable installation standards. This sizing ensures that there is sufficient strength and stability to support guy wire applications effectively, particularly in outdoor plant settings where environmental factors can impact installation.

Choosing the correct size is crucial for ensuring that the guy rod can adequately support the anticipated loads and perform reliably over time in varying weather conditions. The other options do not correspond to the metric equivalent of a 5/8" rod in a standard way, making 12M the most suitable choice.