Stud and nut set, cylinder head and barrel for Norton early iron head twins. Front stud nuts have 1/2 in AF hex, as it is easier to obtain or make a reduced 1/2 inch adaptor than grind down a good BSF one. The rear nut is 3/8 BSF. Original parts numbers: D12/977; T2104 - Cylinder head and barrel stud (fr & rr) 3/8in x 3 D12/E3224 - Cylinder head and barrel stud nut rear x 1 D12/978; T2034 - Cylinder head and barrel stud nut fr x 2 5/16 D12/974; E5376 - Cylinder head and barrel stud nut washer x 3