Did you know a straight through muffler - glass or otherwise - is illegal on Federal Lands (Forest Service and BLM,) on many State Lands, and often against the law in many cities?
Reason is fire - red hot pieces of carbon can fly straight through and cause fires. When the hot particles have to twist and turn around baffles by the time they come out they are cooler.
Get caught with them in some areas the Forest service will not only arrest and fine you, but charge you to have it flown out by helicopter (at least that's what they tell you.)
In addition to the fact they make too much noise, especially after a few miles.
A quality Turbo muffler has no more restriction, is legal, safe, cheap, and has a deep non-deafening sound. They last much longer too.