4394756, 4394756RX | Genuine Cummins® Module, Inlet Catalyst for Epa17, ISX/QSXDescription: Module, Inlet Catalyst Condition: New Brand: Cummins Part Number: 4394756, 4394756RX Fits For: Epa17, ISX QSX Engines The Inlet Catalyst Module 4394756RX also known as the Diesel Oxidation Catalyst (DOC), is the critical first stage of the "Single Module" aftertreatment system used on large bore Cummins engines like the X15, ISX15, and QSX15. Key Characteristics: The "Furnace" of the System: Its most important job for the 15 liter engine