Seamless pipes are a type of welded steel pipe, referring to pipes where the weld seam is parallel to the longitudinal axis of the pipe. They are categorized by wall thickness into thin-walled and thick-walled seamless pipes; by shape into round, square, or other-shaped pipes; and by application into general welding pipes, galvanized welding pipes, oxygen welding pipes, wire conduit, metric welding pipes, roller tubes, deep-well pump pipes, automotive pipes, transformer pipes, welding thin-walled pipes, welding non-standard pipes, and spiral-welded pipes.