Intelligence, surveillance, and reconnaissance (ISR) sensor technologies have evolved as mission requirements become much more rigorous. As this technology has evolved, the demands have increased for the highest levels of performance and reliability in high-precision windows. These ISR windows must demonstrate superior performance in order to avoid compromising a mission’s success. Sapphire is extremely durable, scratch-resistant, withstands extreme temperatures, and transmits over a broad wavelength range of light, making it an excellent choice for ISR optical windows. This white paper discusses the important criteria for selecting a sapphire window manufacturer for high-reliability ISR applications.