Replacement mirror kit 1085931-002 is a routine maintenance kit designed for use with MultiGas 203X/603x Fourier Transform Infrared (FTIR) gas analyzers having a 70mL gas cell volume. This kit inlcudes a gas cell objective (back) mirror with a 5.11m pathlength perscription and MgF2, corrosion resistant, coating in addition to a replacement 1073822 Kalrez oring seal.