Stainless steel cap nuts are essentially stainless - steel hexagonal nuts with a cap. The cap is used to fasten the exposed part outside, which can prevent external impurities, moisture, or other corrosive substances from entering, play a rust - prevention role, and thus prolong the service life of the nut itself and the connected components. In addition, in some industrial machinery that often comes into contact with the human body, using stainless - steel cap nuts as bolt cappings can reduce the mechanical damage to the human body.