Pipes of metal, especially steel pipes, piping of metal, especially of steel, penstock pipes of steel for the transport of crude oil and/or natural gas, pipe connection pieces of metal, like of steel, especially for crude oil pipelines or natural gas pipelines, gas-tight threaded connection pieces of metal, like of steel, especially for crude oil pipelines or natural gas pipelines, pipe connection pieces of metal for piping, pipe systems of metal consisting of strings of metal pipes, metal pi...