Also known as acorn nut or dome nut. Safe rounded head hex nut used in areas of a bike that are open to possible injury from sharp edges .A dome or acorn nut is also called a cap nut. They protect and hide the screw or bolt threaded end. Excellent for decorative or finish work. Pike nuts are almost the same but more pointed .These nuts are a must for finishing off exposed thread on stud work such as engines bolts, foot pegs or other bolt on accessories