Facet added stainless steel internals to its line of pumps to accommodate Tier 4 diesel engine requirements. The engine manufacturer specifies that any brass components be replaced with stainless steel.
The only parts affected are the fuel chamber and check valve, and these parts are made with stainless steel in the new steel internals pumps.
As for other pumps components, they are either already stainless or they are made with compliant materials that are unaffected.
Unless you are working with a Tier4 diesel engine, stainless steel internals are not necessary.