This product is also known as stainless steel capillary tubings . It is mainly used for downhole capillary pressure measurement of oil and gas, that is, temperature and pressure sensors (also known as downhole permanent pressure gauges, generally nitrogen gas cylinders) and oil and gas well production pipe are lowered into the oil and gas layer thousands of meters deep underground, and then 1/8" hydraulic control pipeline (capillary) is connected from the temperature and pressure sensor to the surface of the fluorescent screen display. In this way, the downhole temperature and pressure can be transmitted to the surface through the capillary tube, and the instantaneous temperature and pressure at the oil and gas layer can be read out through the fluorescent screen of the surface display, so as to realize the real-time monitoring of the downhole temperature and pressure. It can also be used for pressure control of surface safety valves and other surface valves, as well as various connection pipelines of large equipment instrument control systems for oil and gas field drilling and oil production.