These jaws come as NOVA chuck standard versions (excluding NOVA Titan). These versatile all round jaws get you started. They will handle both bowl and spigot projects. The 50mm Jaw expands into a recess between 51mm and 72mm diameter. When gripping a spigot the range is 42mm to 64mm diameter. These jaws will also hold square stock between 31mm and 52mm. Standard on both SuperNova2 and Nova G3 chucks (except SN2 companion).