An acorn nut is a nut that has a domed end on one side. When used together with a threaded fastener with an external male thread, the domed end encloses the external thread, either to protect the thread or to protect nearby objects from contact with the thread. In addition, the dome gives a more finished appearance. 18-8 stainless steel is very corrosion resistant, strong at high temps and have a minimum tensile strength similar to a Grade 2 bolt. Hi-Line carries 18-8 stainless steel Acorn Nuts in various sizes.