Inter. The whistle corresponded perfectly to the original. Warning, Amazon's garage program doesn't seem to work with exhaust systems. He told me that this pipe is not suitable for my truck. I realized something was wrong when I got two other inter-walkers. Pipes are not the same. When I looked at the diagrams on the Walker website showing the exact tubes for my truck, I found that the Revain shop program didn't use wheelbase to determine which tube would fit my truck, although I did added system. Just a word of caution, use the Walker charts on their website to ensure you have the correct tubes for your vehicle.