23 [ MACHINERY, TOOLS, AND PARTS THEREOF-NAMELY, "CHRISTMAS TREES" AND DISTRIBUTION MANIFOLD ASSEMBLIES OF VALVES AND FITTINGS SOLD AS A UNIT FOR USE IN CONNECTION WITH OIL AND GAS WELLS, CASING HEADS AND HANGERS AND TUBING HEADS AND HANGERS FOR OIL AND GAS WELLS, UNIVERSAL JOINTS FOR VALVE STEM EXTENSIONS, GREASE GUNS AND LUBRICATOR FITTINGS THEREFOR FOR LUBRICATION OF SEATS AND STUFFING BOXES OF VALVES, VALVE STEM WRENCHES, AND ] VALVES WITH POWER UNITS FOR OPERATING THE VALVES