Yarn in rubber hoses serves as reinforcement, providing strength, flexibility, and pressure resistance. It is applied in braided or spiraled layers between rubber sheets. Common types include polyester for strength, stability, and cost-effectiveness; nylon for abrasion resistance and flexibility in high-pressure hoses; aramid (e.g., Kevlar) for exceptional strength, heat resistance, and light weight in demanding applications; and cotton for softness and compatibility with natural rubber in low-pressure hoses. The yarn’s quality, twist, and denier influence hose burst strength and flexibility. Proper yarn selection ensures the hose meets its intended pressure, bending, and environmental performance requirements effectively and safely.