When selecting magnet buttons, the most critical factor is the magnetic flux density (measured in Gauss) and the pull force. For heavy-duty bags, a pull force of 1.5kg to 3.0kg is standard, while lightweight garments require a lower force to prevent fabric tearing. You must also specify the magnet material, typically Neodymium (NdFeB) for high strength-to-size ratio or Ferrite for cost-sensitive projects. Additionally, ensure the electroplating thickness (e.g., hanging plating vs. rolling plating) is sufficient to pass a 24 to 48-hour salt spray test to prevent rust in humid environments.