The container liner is a critical component in aluminum extrusion, directly influencing process efficiency, product quality, and tooling lifespan. This article examines the design, material selection, and failure mechanisms of extrusion container liners. It highlights the advantages of premium hot-work tool steels (such as ESR H13) and nickel-based superalloys for high-temperature, high-pressure applications. Key engineering features—including dual-phase shrink-fit design and optimized surface finish—are discussed alongside common failure modes like thermal fatigue and abrasive wear. The article concludes with maintenance best practices to extend liner life, reduce downtime, and optimize overall extrusion performance.