Nickel Round Bar Invar 36 is a round bar made of Invar, an iron-nickel alloy containing 36% nickel. This alloy has an exceptionally low coefficient of thermal expansion, making it dimensionally stable over a wide temperature range. It is commonly used in applications requiring precise measurements or tight tolerances that must be maintained despite temperature fluctuations, such as in scientific instruments, measuring devices, specialized machinery components, and precision pendulum rods.