This is a genuine GM OEM Duramax Diesel oil cooler assembly. The Duramax engine oil cooler is not normally a component that goes bad, but should be replaced after any catastrophic engine failure or during any performance engine builds
The factory oil cooler has a stack plate design which makes cleaning any debris can be nearly impossible. This is the reason we always recommend replacing the oil cooler.
A defective engine oil cooler is also a major source for coolant/oil cross contamination. Check your coolant degas bottle for a layer of oil. If any appears, it is often defective oil cooler.