Size 8 gauge, or 8G, jewelry, is a mid-thickness gauge that can be used in any body piercing. While there are standards based on the piercing location and individual body types, a piercing can be stretched incrementally to accept almost any gauge.
Gauge is the measurement used by the American Wire Gauge scale, which correlates a gauge size with a measurement of width. The size 8G corresponds to roughly 1/8 inch wide. Gauge is also used in the Standard Wire Gauge scale employed by some jewelers. While the notation is the same, the measurements are not and can vary significantly.