API Spec 5CT Casing and Tubing, Eleventh Edition, Includes Errata 1 (2024) Errata 2 (2024), Errata 3 (2026), and Addendum 1 (2025)

About this publication

The API Specification 5CT, Casing and Tubing, 11th Edition is one of the petroleum industry’s core technical specifications for the manufacture and supply of steel casing and tubing used in oil and gas drilling and production operations. Published by the American Petroleum Institute (API), this edition establishes technical delivery requirements for tubular products that play a critical role in well construction, production integrity, pressure containment, and the safe management of hydrocarbons and other formation fluids.

API Spec 5CT covers steel casing, tubing, pup joints, coupling stock, coupling material, and accessory material. It provides requirements and dimensional information covering items such as pipe sizes, masses, wall thicknesses, grades, and applicable end finishes, giving manufacturers, operators, engineers, inspectors, and procurement teams a standardized framework for specifying and verifying oil-country tubular goods.

The importance of API 5CT goes far beyond pipe dimensions. Casing and tubing serve as critical primary and secondary containment barriers throughout well construction and production. Consistent manufacturing requirements are therefore essential for maintaining well integrity, protecting personnel and equipment, and reducing the risk of uncontrolled releases or other failures in demanding oilfield environments.

The 11th Edition introduced an important structural change from the previous edition by removing the former Product Specification Level (PSL) structure. API states that requirements previously associated with PSLs were either incorporated into the main body of the specification, converted into supplemental requirements, or removed. Products manufactured for API Monogram purposes on or after the applicable transition date must therefore be evaluated using the requirements of the 11th Edition rather than the older PSL framework.

This listing incorporates the subsequent API corrections and technical updates issued for the 11th Edition, including Errata 1 dated May 2024, Errata 2 dated August 2024, Addendum 1 dated May 2025, and Errata 3 dated June 2026. That revision history matters enormously for companies working from controlled standards libraries, manufacturing specifications, inspection procedures, and API Monogram requirements, because relying on the December 2023 base document alone can leave later corrections or requirements out of the working reference.

Addendum 1 introduced several notable updates intended to strengthen casing and tubing manufacturing requirements. API identified enhancements including provisions for high-collapse products with enhanced performance ratings, the addition of new pipe grade C125, new requirements for end sizing and thermal recovery, clarification of end drifting, revised treatment of welded-product retesting following a failed flattening test, and corrections carried forward from differences between the 10th and 11th editions.

These changes make the updated 11th Edition especially relevant for tubular manufacturers, oil and gas operators, drilling contractors, quality departments, third-party inspectors, engineering firms, and organizations participating in the API Monogram Program. It provides a current technical basis for purchasing specifications, manufacturing controls, inspection programs, quality documentation, and acceptance of casing and tubing products used throughout well construction and production.

At approximately 151 pages in the base 11th Edition, API Spec 5CT is a concentrated but highly consequential petroleum-industry specification. For anyone responsible for OCTG manufacturing, procurement, quality assurance, inspection, or well integrity, it is a core working standard rather than a general reference title.

Why This Standard Matters

API Spec 5CT, 11th Edition is a key reference for organizations involved in the manufacture, selection, procurement, inspection, and use of casing and tubing. It is especially valuable for:

• Oil and gas operators

• Casing and tubing manufacturers

• OCTG suppliers and distributors

• Drilling and completion contractors

• Petroleum and well engineers

• Quality assurance and quality control teams

• Third-party inspection organizations

• API Monogram licensees

• Procurement and technical specification teams

• Well-integrity and production personnel

Product Features

• Official API Specification 5CT, 11th Edition

• Covers casing, tubing, and pup joints

• Includes requirements for coupling stock, coupling material, and accessory material

• Addresses pipe sizes, masses, wall thicknesses, grades, and end finishes

• Establishes technical delivery conditions for steel tubular products used in oil and gas wells

• Supports casing and tubing used as important containment barriers

• Incorporates requirements relevant to manufacturing, inspection, testing, and product acceptance

• Reflects the 11th Edition transition away from the former PSL structure

• Includes Errata 1 — May 2024

• Includes Errata 2 — August 2024

• Includes Addendum 1 — May 2025

• Includes Errata 3 — June 2026

• Addendum 1 adds provisions for high-collapse products

• Adds new C125 pipe grade

• Includes updated requirements for end sizing and thermal recovery

• Clarifies end drifting

• Updates requirements involving retesting of welded products following failed flattening tests

• Important reference for API Monogram manufacturers and quality systems

Product Details

Title: API Specification 5CT — Casing and Tubing
Publisher: American Petroleum Institute (API)
Edition: 11th
Published: December 2023
Base Publication Length: 151 pages
Product Number: G5CT11
Includes: Errata 1 (May 2024), Errata 2 (August 2024), Addendum 1 (May 2025), and Errata 3 (June 2026)