Universal stud made for fitting the HS4/HIF carb to the manifold (except HS6 with alloy spacer on cast one piece manifold which requires CHS2515 (5.8mm longer)) and it also fits the cylinder head to take the thermostat housing. Note that HS2 carbs require larger CHS2613/4 studs. 5/16\” unc and unf at nut end, this stud is about 4.5cm long about 3.5cm from the bottom of the UNC thread. Nut to suit is GFK3212 & spring washer is GFK1125.