AN Bolts in different series are manufactured to the "Army-Navy" military standard (predecessor to "Mil-Spec" (MS) and "National Aerospace Standard" (NAS) which followed). They can be used for either tensile/shear load applications throughout the aircraft. They are offered in different materials, surface finishes, diameters and lengths (see table below). AN3 through AN20 Series bolts are superseded by NASM3 through 20 Series. The part numbers in both series have not been changed.
They are available in high-strength type 4037 or 8740 alloy steel and 431 Stainless Steel (CRES) versions with drilled or undrilled shank. AN bolts with undrilled shank are specified by letter "A" after the dash number. AN stainless steel bolts are specified by letter "C".