Fluid leakage costs industry millions of dollars every year. In addition to wasted money, unattended leaks can result in downtime, affect product quality, pollute the environment, and cause injury. Successful sealing involves containment of fluid within the system while excluding the contaminants; the resilience of rubber creates a tight sealing effect, containing fluid and excluding contaminants. A sound understanding of the complex factors involved in successful fluid sealing is essential for engineers who specify, design, operate and maintain machinery and mechanical equipment. This book focusses on the characteristics of rubbers as seals, their manufacturing procedures, the implications of their physical and chemical characteristics for the sealing function in the fluid and hydraulic systems, how rubbers seal and prevent leaks, what properties are required for sealing function, and how they change before and after installation.