Rola Chem ORP Probe [Digital Analog Ctrl Sys Heavy Duty 8ft] (550136) repairfittings Kit format supports more complete Kit format supports more complete repair work Lock knobs are useful because they give the user a direct way to secure or release the associated component without relying on improvised tools or damaged original hardware Rola Chem ORP Probe [Digital Analog Ctrl Sys Heavy Duty 8ft] is a heavy duty ORP probe for compatible Rola Chem digital and analog control systems it helps monitor oxidation reduction potential so automated chemical controllers can respond to sanitizer demand and support consistent water treatment performance