I really thought the factory tips were smaller, but I guess it's in the details. My Greddy is 4.5", but they're also straight cut. Inside diameter is notably larger, and I guess just gives the illusion of being bigger overall.
Here's a few examples of the 5" so you can get an idea. In speedfreek's post, you can see what I'm talking about in reference to the illusion of the straight cut appearing larger.
exhaust tips