Oh, forgot to answer your other question - the ones I have now have the same design as yours - there are a series of baffles inside and a plate at the end with a cone to direct the exhaust outwards through the baffles. Mine also had a set of internal flappers to prevent water from washing up the pipe. The bigger ones without the angle cut use an external salisbury flapper to help prevent water intrusion.

I told you wrong. You can't see through the mufflers so I didn't know.

The previous owner had metal flappers in the exhaust tubing. I switched tips. Good thing I did, one of my flapper pins were broke.