The range listed is in imperial units (inches), with UNC threads. The large view below shows types of bolts. For thread chart, click here.
In copper and bronze and brass.
In imperial sizes, see here for a gauge chart and pilot hole info. Please don't use brass screws for bronze fittings.
Like brass, listed in imperial sizes guaranteed to confuse everybody brought up on the metric system. See click HERE for a gauge chart and pilot hole info. We can source many more sizes than are listed.