Model 3004 retractable process probes provide flexibility and economic replacement via probe inserts. They employ sensing elements made from wire, strip, or small diameter tubing, formed into a hairpin loop. Alloys and element styles normally available are listed in Table 1. Other alloys or element styles may be subject to material availability. These probes may be used up to their design temperatures and pressures in organic or inorganic fluids of all types, in the pH range 0-9. Above pH 9 or for other extremely aggressive service, Model 3504 Probes are recommended. In applications where stainless steel bodies would be subject to failure due to stress cracking or severe pitting, or for probes made of special materials, contact the factory for specific information before ordering. Probes specified by a complete probe order number include both a housing body for mounting and a replacement measuring element insert. The insert may be ordered separately as needed.