They fit on the 3" outlet pipe on the Thermal R&D mufflers near the raer bumper. If they were black I would take them to a fabrication shop and have the guy band saw off the 3" inlet and weld on whatever size inlet needed in 304 stainless steel. I originally purchased black ones to do this. I was going to add them to my Thermal 2.5" exhaust. Then I decided to get the Thermal 3" exhaust with polished tips so I had both tip colors so I could swap them out if I wanted. Then I ended up trading my 2020 ST in on a new 2023 ST. Decided I didn't want the 3" Thermal and sold it new in the box but the guy wanted the black tips instead. So that's how I ended up with Thermal 3" new style polished tips. So they have an inlet that fits a 3" exhaust pipe. The outlets are 4" each. They are about 10.5" long to the furthest staggered tip. To fit a smaller exhaust pipe than 3" you would have to modify the inlet end.