Dynomax has revised this model. What I can't say about others. The newer model does not have flow guides as shown in the picture. This model now has a long entrance (labeled INLET). The protrusion at the end of the muffler acts as a guide and then returns to the chamber and exhaust port, forming a little S-shape as it were. I used a mirror to check this. You can find old stocks with old designs. I want companies to update their information. As a consumer, I want what I pay for. Good luck folks.