The Thread Adapter has an outer thread size of M20x1.5mm. The inner thread sizes available are: M8x1.25mm, M10x1.25mm, M10x1.5mm, M12x1.25mm, M12x1.5mm, M12x1.75mm, 5/16"-18, 3/8"-16, 7/16"-20, 1/2"-20 and 9/16"-18.