Gauge: Thickness of the part of the piece that passes directly through the piercing.

• Measured by a gauge sizing tool or gauge card, a caliper, or by a piercer

Diameter: Measurement across the opening of a circle. Remember that this is the measurement across the opening, and does not include the outside of the circle itself. This is why you may hear it called the "inside diameter" of a piece. You are only measuring the open space.

• Measured with a ruler, caliper, or pencil and paper, drawing a straight line between two inside sides of the circle and measuring

Length: Distance from tip to tip of the wearable portion of a piece.

• Measurable by ruler, or using a pencil and paper, by laying an item flat, and making a mark at either end of the wearable portion of the piece, then measuring the distance between them.