Body piercing barbells are usually between 8mm and 10mm in length,
This measurement is taken front to the back of the piercing, so when measuring jewelry such as a labret stud or barbell piercing, the measurement does not include and thread, balls or attachments. In the case of a ring, the diameter measurement is the internal measurement.

Gauge (Thickness)
Tragus piercing or Helix piercing: The most common gauge (thickness) of jewelry worn is 16 gauges (1.2mm)
Labret Monroe piercing stud: The most common gauge (thickness) of jewelry worn is 14 Gauge (1.8mm) or 16 Gauge (1.2mm)

Labret piercing usually refers to a piercing that is below the bottom lip and above the chin.

Tragus piercing is referred to as the small oval cartilage flap located right outside the ear canal.

Medusa piercing is quite similar to the labret but can instead be centered below the nose, above the top lip's "cupid's bow."

Labret studs are a great choice for tragus earrings because of the smooth back flat disc with internally threaded rather than a ball that screws on the back, which can be sometimes uncomfortable.

Take this barbell piercing that can be fit as Labret stud, Monroe piercing jewelry, Tragus earrings, or Helix earrings featuring a sparkling crystal for extremely fashion-conscious people and willing to try different things to maintain a look that is unique and distinguishable from others.