Pull the rubber o-ring off the old gasket.
But for my nickel, if it don't say Mopar or Cummins, I don't think I want it.
I got one from AutoZone before I knew better. Cheap looking thing with a paper gasket. Went to the $tealership and paid $27. 95 + tax. When I compared the two, I returned the AutoZone stat. No way would I trust my expensive Cummins to an after market stat.