Under the ISO 3506 standard, "A4" designates the austenitic stainless steel group alloyed with Molybdenum (which corresponds to SS316 / 1.4401). The "80" indicates the property class, meaning the fastener has been cold-worked to achieve a minimum tensile strength of 800 MPa and a minimum yield strength of 600 MPa. This provides significantly higher load-bearing capacity than standard A4-50 or A4-70 fasteners.