"Size","UNC (TPI)","UNF (TPI)","Head Ø","Head height","Hex key"
"1/4″ (6.35)","20","28","0.375″","1/4″ (6.35)","3/16″ (4.76)"
"5/16″ (7.94)","18","24","0.469″","5/16″ (7.94)","1/4″ (6.35)"
"3/8″ (9.52)","16","24","0.563″","3/8″ (9.52)","5/16″ (7.94)"
"7/16″ (11.11)","14","20","0.656″","7/16″ (11.11)","3/8″ (9.52)"
"1/2″ (12.70)","13","20","0.750″","1/2″ (12.70)","3/8″ (9.52)"
"5/8″ (15.88)","11","18","0.938″","5/8″ (15.88)","1/2″ (12.70)"
"3/4″ (19.05)","10","16","1.125″","3/4″ (19.05)","5/8″ (15.88)"
"7/8″ (22.22)","9","14","1.313″","7/8″ (22.22)","3/4″ (19.05)"
"1″ (25.40)","8","12","1.500″","1″ (25.40)","3/4″ (19.05)"
"Reference only — confirm against drawing. ASME B18.3. REL India"