No pollution, Health lead-free environmental protection non-toxic. STANDARD SIZE(Tolerance:0.005mm): Uniform force, located in the center of the head with no offset, not easy to slip; Uniform pitch, obvious screw thread, no residual burrs, the set screw threads will be able to get a good grip. PLASTIC HEAT SEAL PACKAGING: Practical and convenient of packing box, All of screws and nuts are packed in a durable and sturdy box, this box can be use for a storage box. Please be sure to read the description thoroughly to make sure that this is the item you want before making a purchasing decision. Please be aware that slight variations in color may be due to differences in lighting and computer monitor resolutions. Boxes or APOs. An adult signature will be required. Please be sure to have available help on hand to assist you with moving the item to the desired location in or outside of your home. You can request a refund if you are dissatisfied for any reason with your product. Only factory defects are accepted as a reason for a return. The item and package should be in original and perfect condition.