Oil tubing is a critical string in oil and gas extraction. Regarding specifications, it is characterized by outer diameter (e.g., 60.3 mm, 73.0 mm, 88.9 mm) and wall thickness, conforming to the API Spec 5CT standard. **Steel grades** indicate strength, with common examples being J55, N80, and P110. The numbers represent the minimum yield strength (in thousand pounds per square inch, ksi); for instance, grade P110 has a minimum yield strength of 110 ksi. **Connection types** are mainly divided into API connections and premium connections. API connections include **NU** (non-upset) and **EU** (external upset), with the latter enhancing connection strength due to the upset end. Premium connections utilize a metal-to-metal seal, offering superior gas-tightness and fatigue resistance. In terms of **performance**, the tubing must possess high tensile strength, internal pressure resistance, and corrosion resistance to accommodate complex downhole conditions.