METRIC DIN 912 ISO 4762 BS 4168-1
SOCKET CAPS SCREWS ARE MEASURED FROM UNDER THE HEAD.
GRADE 12.9 HIGH TENSILE STEEL BLACK PHOSPHORUS.
GRADE 12.9 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.