The Fleetguard FF5825NN is rated at 5 microns absolute (β₁₀₀₀ per ISO 19438), using NanoNet synthetic media. The "NN" suffix in the part number marks the synthetic media upgrade from the older Fleetguard FF5776 plain-paper version. At 5 microns absolute, the filter captures particles small enough to protect the high-pressure common-rail injectors on Cummins ISX, ISX15, and X15 engines, where injector tolerance is the binding constraint. Steinberg's FF006 matches the same 5-micron spec and ships from our Hodgkins, Illinois warehouse, same-day for orders before 2 PM CT. For comparison, a 30-micron filter would let through roughly 36 times more particle volume per gallon, which is why micron rating matters more than filter price when injector replacement runs $11,000 on an X15.
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