Sailboat parts, hardware and equipment products are specified in both imperial and metric measurements. In most cases, the metric dimension shown is calculated from the imperial measurement and rounded to a whole number. For example, 5/16" is generally shown as 8 mm, while an exact conversion would be 7.9375 mm. When referring to a line diameter, it is sufficient to approximate the conversion. In cases where a dimension is critical, exact metric dimensions are normally preferred over imperial or SAE measurements.