OK this may seem to be a stupid post but I just need someone to tell me what the difference between a glass pack and a muffler.

 

A glasspack is a kind of automobile muffler in which the exhaust gas passes straight through the center of the muffler. Packed fiberglass surrounds the exhaust channel and absorbs some of the high-frequency sound. so it basically looks like a long cylindrical tube.

A muffler typically has a series of chambers or baffle plates to reduce noise. The exhaust does not pass straight through like it does in a glasspack.