Material:Metal + Plastic. Size:2.5x2x2.3cm/0.98x0.78x0.90in. The MH-Z19C carbon dioxide gas sensor (hereinafter referred to as the sensor) is a general-purpose smart small sensor that uses the principle of non-dispersive infrared (NDIR) to detect the presence of CO2 in the air and other functions. Built-in temperature compensation: It has serial output and PWM output at the same time, which is easy to use. The sensor is a high-performance sensor that combines mature infrared absorption gas detection technology with precise optical circuit design and precise circuit design. Package Includes: 1 Set x Sensor Specifications: Color:Yellow Material:Metal + Plastic Size:2.5x2x2.3cm/0.98x0.78x0.90in note: Please allow a little error on the size due to manual measurement. The color might exist slightly difference due to different displays.