.067

This is probably a .067 inch (about 1.7 mm) electric bass string. Electric bass strings are generally classified by gauge, which is the thickness of the string in inches or millimeters.

.067 inch bass strings are considered quite heavy and are often used for basses tuned to B or C#. However, it is important to note that the choice of bass string gauge is a matter of personal preference and will also depend on the style of music you play and the sound you are looking for.