This one is nearly identical and half the price, both made by Walker but the dynomax has rounded baffles at the ends that "guide" the exhaust flow.
Interesting, I found the Thrush at the local Advance Auto and there is no Dynomax labelling, I think that's a Summit goof. In any event, I put a 2.25" on mine, side swept in front of the rear wheel and an Amsoil cone filter and it's still almost as quiet as stock, a little dissappointing. The muffler was $20 so I think I'm going to go back to flowmaster (had a 40 series original on my Explorer which is mean sounding in comparison) if this thing doesn't wake up. It's been 1000 miles or so already though. Flow is definitely improved over stock though.