We have two that look and function really well. The Silverline double wall SS tip clamps onto your 4" tail pipe and the outlet is a tapered plend from the 4" to 5" transition you see. The other is the Big Dog double wall resonator tip. This one is welded on and is much like the Silverline with the blended taper transition, but also the inner portion is perforated with packing between the 4" and 5" walls. Some guys say this makes a difference in the sound of the exhaust. You can see some pictures here http://www.dieselpowerproducts.com/exhaust

 

I had it welded on....too expensive to band-clamp it and take a chance on it mysteriously vanishing from my truck !
Greg