The rest of my nickel:
I have yet to see a single aftermarket exhaust that didn't look like it was made to fit --- you pick:
A riding mower
A tractor
A roof-top A/C unit
A terrorist's homemade F-150 with gun mount
Any one of 123 different Asian scooters, generators, 4-runners, snow blowers - any size motor, any color
My neighbor's turkey smoker
What I have never seen is an after-market exhaust "can" that looked like it ever came within a kilometer of an Italian, Asian, German, or American design studio. To actually design and 'sculpt' a muffler for each application is beyond the capability of any of these shiny tube makers, armed with the weld torch and home-made pipe bender. They'll whip you one up for @ $100 US and a carton of Marlboros.
I once ran a Honda bike all over southern California with an after-market exhaust. It was a Hunts tomato sauce can with nail holes. At least it was red and color coordinated with the red bike. (until the label burned off)
Bless the folks that are big enough to admit that these one size fits all shiny cans have NOT increased anything but the noise of their scooter....and that they are glad they kept the stock muffler under their beds so they can switch back.
Going to odd lots and buy a Thrush 'performance' muffler soon as I get done here. They come in 2 sizes so you can get the best from your car,truck, boat, plane, A/C unit, turkey smoker - foreign or domestic.
Stig