Sturdfix Hex-bolt, Standard : DIN 931-933-ASTM A325-A490

Hex-bolt 8.8-10.9-12.9-
(din 931-933-astm a325-a490)rnan acorn nut, also referred to as crown hex nut, blind nut, cap nut, domed cap nut, or dome nut (uk), 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 of the threaded fastener, either to protect the thread itself or to protect nearby objects from contact with the thread. In addition, the dome gives a more finished appearance.
acorn nuts are usually made of brass, steel, stainless steel (low carbon content) or nylon. They can also be chrome plated and given a mirror finish.