[PRODUCT SIZE] Inside Diameter: 3/8 inch [DURABLE AND CORROSION RESISTANT] Our acorn cap nuts made of high-quality 304 Stainless Steel, which is superior to regular steel and has higher corrosion resistance than ordinary washers. It has longer service life, not easy to damage, more solid in bad environments [VALUE PACKAGING] This package contains 20 pcs nuts, it storages in a plastic box. You can get your work done easily and qucikly. They are ideal for use at home, in the office or at work. [APPLICATIONS] Acorn cap nuts are used to secure threaded bolts and screws in place, providing strong clamping force, preventing loosening under vibration, and ensuring a stable, reliable assembly. [INTIMATE SERVICE] We focus on customer satisfaction, if you have any questions or are not satisfied, you can contact us by email, we will solve all your problems as soon as possible.