Like it says! They are the same flathead design motor. What did you make and how did you make it? Lets see your handy work! ( selfish motive working on one now for a BTR build )
It is not a whiskey flask but it does look like one.
It is basically a mini version of a car muffler, it has baffles inside to dampen the sound. I wanted the bike to be kinda stealthy and not draw attention from cops.
The stock muffler box was quiet but it blew the exhaust right out on your leg.