Ordinarily, up to now you have relied on a cone to attach flue gas probes to the flue gas pipe and to hold them in the centre of flow. However, this meant that the probe was often unsteady in the pipe and might also lose the centre of flow. With the new testoFix probe holder, this is no longer a problem. Thanks to a cleverly devised mechanism, this is fastened securely to the measurement aperture in two easy steps. Shaky probes are therefore a thing of the past. You can also use the testoFix probe holder to attach the testo 330i flue gas analyzer directly to the flue gas pipe. The testoFix probe holder is suitable for probes with a diameter of 8 mm and all measurement apertures with a minimum diameter of 10 mm and a maximum surface temperature of 140 °C. Scope of delivery testoFix probe holder. testoFix-Sondenhalterung. Use the patent-pending testoFix probe holder to attach flue gas probes to the flue gas pipe quickly and securely – no tools or cone required. This global innovation, which was developed by Testo, also serves as an attachment system for the testo 330i flue gas analyzer.