Each individual copper - plated cap nut is first placed into a high - density polyethylene (HDPE) plastic bag. These bags are typically 0.03 - 0.05 mm thick, providing a basic level of protection against minor scratches, dust, and moisture. The bags are heat - sealed to ensure a tight closure, preventing the cap nuts from moving around and getting damaged during transit. For example, for a batch of M6 copper - plated cap nuts, the size of the plastic bag is customized to fit the nut snugly, with a small margin to allow for easy handling.