Will this exhaust fit? What is stock diameter?

[nuts4hotwheels]

I am thinking about buying a kit on eBay but I am unsure of the fit on my vehicle. I have a 2001 Ram 1500. The listing states

Performance Dual exhaust system

This system will turn your factory exhaust into a performance dual exhaust. These are a basic kit that will include everything from the muffler to the bumper . The unmistakable deep rumble will give your truck the sound of a performance muscle car . They feature 2.5" mandrel bent pipe that are aluminized to increase life

Kit includes

Performance high flow Flowmaster Super 44 series w/ a Single 3" inlet dual 2.5" outlet
US made aluminized multi piece tail pipes 2.5" mandrel bent
4 Multi depth rubber insulated hangers
9 muffler clamps in 2 1/2"
All connections are slip fit (no cheap couplers)

 

[dapepper9]

2" from manifolds that merges into 3" inlet for the cat that necks it back down to 2.5" that goes to theymuffler and after the muffler it expands back up to 3" for the tailpipe

 

[nuts4hotwheels]

So, I guess I would need a coupler to go from 2.5" to 3" for the muffler.

 

[dapepper9]

Or run 3" from the cat to the muffler.