Hey frame builders without machine tools. It's always driven me nuts how hard it is to find tools if you aren't a machinist, but still want to make frames. So we had our friend Travis At Cooper Cycles Lathe us up some Dummy Headsets.
Then drilled and tapped them M6, added a stainless thumb screw and polished them up.
They have been precisely machined to slip fit into a frame that has been faced out for ISO, so no need to press them in, but everything holds firmly for working on racks or keeping the frame-set together while working or storing it.