The Walker Dynomax is aluminized mild steel. There are other systems out there that are plain mild steel, which is worse yet.
The original equipment pipes are heavier gage steel, and at least the front part is 409 stainless.
The original muffler I removed from my F450 weighed half again what the Walker replacement did.
There are several aftermarket systems which claim to be some variety of stainless steel. Unfortunately, most of them are obnoxiously loud, and would be at home in a high school parking lot.
