Hole size needed for the 32mm Bulkhead threaded end to be drilled is = 42mm min / 50mm max. Hole size needed for the 50mm Bulkhead threaded end to be drilled is = 60mm min / 70mm max. Hole size needed for the 20mm Bulkhead threaded end to be drilled is = 26.5mm min / 32mm max.
eBay