were some quality issues right away. The welds on the inside were not ground down and were very jagged and looked like they would impede the flow of air (I had a friend grind them down so that wasn't a problem anymore but it was still disappointing) Also after driving a while I could see that the metal started to become discolored because of the heat. I'm not sure if this happens with the SZ ones but probably shows that they use lower quality metal as well. Stick with the SZ ones and you will be happier knowing you have a higher quality product and knowing that you're helping out a true innovator for the Z community.