Thermo Scientific Part 4119 – Capillary, 08 Mil (Red), original flow restrictor capillary designed for Thermo Model 42i, 42i-D and 42i-LS NO / NO₂ / NOₓ chemiluminescence gas analyzers. This red 08 mil capillary controls ozone flow inside the reaction chamber, critical for stable NOx measurement, EPA ambient air quality monitoring, CEMS and stack gas monitoring systems