... Drilling Rod: made by CNC, and multi-heat treat, with premium alloy steel ... ltd., is the professional manufacturer of drilling tool in china, and specializing in the design ... reaming shells, overshot, hoisting plug, water swiel, wrench. These are all manufactured to the strictest quality ... , PDC) 4.Drill tool: hoisting plug, water swivel, overshot, outer tube & inner tube wrench, foot clamp,etc.