Ink tags are a form of retail loss prevention that is commonly used in clothing stores.
These tags contain glass vials filled with permanent ink and have a thick plastic cover.
[1] The tags are attached to the items they protect with a magnetic lock which requires a special tool to remove.
Ink tags fall into the loss prevention category called benefit denial.
[2] Although the use of ink tags does not prevent the theft of an item, it does strongly discourage it by decreasing the benefit received by the shoplifter.