Home Resource Center Product Data and Related Literature Alloys Precision Strip Precision Strip Resources R270 Typical Properties Data Sheet Materion R270 Resistor Alloy is a Copper-Manganese-Nickel alloy with low resistivity and very low Thermal Coefficient of Resistance (TCR). Commonly used for precision resistors, R270 is produced using a patented casting process, which produces homogeneous alloying and consistent, stable performance.