Parker Tools and Fixings Stair Raked 38 Deg 32nb Galv Ball Standard - 60mm Balls are drilled and tapped and fitted with stainless steel M8 socket setscrews. Base plates are complete with two 18mm diameter holes to suit M16 fixing bolts. Quicker on site assembly with No Welding and with Ball Sizes: 60mm - 25NB / 75mm - 32NB.