PREMIUM QUALITY: These insert nuts are made of high quality galvanized carbon iron material, providing strength and good corrosion resistance in many environments. Features: Insert nuts have advantages over barrel nuts and T-nuts because they can be installed on one side of the workpiece. Easy to Use: These are multifunctional threaded nuts, you can easily drive with them, easy to use. Note: The depth of the pre-drilled holes must be the same as the length of any part of the embedded nut and bolt that can be screwed through the end of the nut into the workpiece. Note: The data are all measured manually, please allow 1-3cm error due to differences in light and display, there may be some color differences, please refer to the actual item received.