This is an essential tool for professional piercers, thanks to their slotted head to insert the needle through.
Small model:

• 5.75" (14.6 cm) long.
• Slotted head of 3/8" (10 mm), a hole of 3/16" (5 mm) and depth of 0.1" (2.5 mm).

Large model:

• 5.75" (14.6 cm) long.
• Slotted head of 1/2" (12 mm), a hole of 1/4" (7 mm) and a depth of 0.14" (3.5 mm).

Both models have a smart locking mechanism.