METRIC DIN N/A ISO 7380 BS 4168
SOCKET BUTTON SCREW ARE MEASURED FROM UNDER THE HEAD.
GRADE 10.9 HIGH TENSILE STEEL BLACK PHOSPHORUS.
GRADE 10.9 HIGH TENSILE STEEL ZINC PLATED.
GRADE A2 = 304 STAINLESS STEEL.
GRADE A4 = 316 STAINLESS STEEL.
UNC BLACK PHOSPHORUS, ZINC PLATED, STAINLESS STEEL.
UNF BLACK PHOSPHORUS, ZINC PLATED, STAINLESS STEEL.
BSF NON-PERFERRED CHECK AVAILABILITY.
WHITWORTH NON-PERFERRED CHECK AVAILABILITY.