Description: (Sizes are the diameter of the hole in the nut splitter)5/16“-1/2” 9 12mm Nut Splitter. Requires 12mm Spanner to tighten.1/2”-5/8”12 16mm Nut Splitter. Requires 14mm Spanner to tighten.5/8“-7/8”16 22mm Nut Splitter. Requires 18mm Spanner to tighten.7/8”-1-1/16“22 27mm Nut Splitter. Requires 21mm Spanner to tighten.45 # steel hot forged shell, inner core bearing steel