They are bolts with cylindrical head recessed key used in cases where the seat of the imbus bolt head is too narrow for the nut wrench to enter, or in cases where the bolt head is not wanted to be left out. Also known as Allen head, hex head or hex head bolts. They are used with an Allen key. Allen wrench is a simple tool used to drive bolts and screws with hex socket heads. The tool usually consists of a single rigid hex rod with blunt ends intended to fit tightly in the screw socket, bent into an 'L' shape with unequal arms.
Imbus: Stainless imbuses, which have many different types such as countersunk, dished-headed, fine-headed; It is frequently used in defense and aviation, boat and yacht accessories, automotive, machinery and chemical industry, medicine, facade systems, dairy and food industry, chemistry, petrochemistry, medical instruments, construction and similar various fields.