I don't know the answer to your question OP. I'd be calling the manufacturer on this one. Anyways, here's what they are saying per the Summit website:
"You've improved your reaction time and now it's time to inform your competition. Proform Perfect Launch differential covers state the facts with their logo machined on the raised reinforcing surface. These rear-end covers are made of lightweight but tough aluminum and have been specifically designed to add strength to the rear housing case, particularly during heavy torque situations. Precision-milled and painted black, these Perfect Launch covers include two bolts to stabilize bearing main caps, two magnetic drain plugs, and mounting bolts. You can lose a little weight in your rear-end and send a message to your competition with Perfect Launch reinforced differential covers from Proform."
They do say the cover adds strength. I would buy that statement. But I would side with
@Schurkey on this. These axles don't usually fail in this area; it's usually ring gear, spider gears, axles, or bearings or something like that..."stabilize bearing caps?" I didn't know those are unstable! Like, do they loose up under load or what!
Now the statement about losing weight is just ridiculous! That stamped steel cover has to weigh ounces. I would be surprised if the chunkier-looking aluminum weighs marginally less. Maybe I'm wrong?
I would make this a good example of how lucrative and profitable the aftermarket automotive industry is. I bet there's marketers from these companies coming up with these ideas. They probably have some internal mission statement that says something like, "...just build it and they will buy it." Sadly, this is true in a lot of our consumer-driven economy. :-(
Sorry, nothing against this product. But it does look cool as heck!