This guide explains the primary components of an injection mold and how they influence part quality, cycle time, mold life, and manufacturing cost. It covers the mold base, cavity, core, inserts, runner system, gates, cooling channels, vents, alignment systems, ejectors, slides, lifters, and common mold-related defects. It also outlines key factors for selecting a mold configuration, including resin choice, annual production volume, part geometry, tolerance requirements, cosmetic expectations, and maintenance needs. A thorough review before tooling begins helps create a more reliable mold and a more predictable production process.