UEI C75 02, CO, STACK, EFFICIENCY, CO2 Measures:Flue temperature, oxygen, carbon monoxide (CO) Calculates: Carbon dioxide, efficiency, excess air, CO air free Unique DMM style rotary selector Protective boot w/integral magnet Real time clock CO readings to 1 ppm Large 2 line back-lit display Infrared printer port User programmable header 20 memory position 3 Year limited warranty (2 Year warranty on sensor) Product Includes C75 Combustion Analyzer Flue Probe Particle filter Owners guide