These Borosilicate blank flanges are designed to withstand temperatures between -15°C and 150°C. They are capable of reaching vacuum down to 7.5 x 10^-9 Torr and are resilient to over pressure up to 375 Torr. For proper pressure vacuum seal they require the use of an over pressure centering ring and must be used in conjunction with only plastic hinge clamps not metal. Centering ring and plastic hinge clamp not provided. These Borosilicate viewports blank flanges are perfect inspection windows and can be used in a variety of applications. Quartz viewports blank flanges are also available for applications requiring higher temperature thresholds.