When designing the glass-to-metal-seals and ceramics-to-metal-seals, if the expansion coefficient of the two materials are similar, it will be called as matched seal. If there is big difference between the two expansion coefficients, it is called as mismatched seal. The matched and mismatched seals are both reliable. Different seals can be applied for different practical conditions. OHMALLOY provides different alloy materials for different seals.