High flow muffler options?

Does anyone know what LR,MR, and HR mean?

 

If you want them to be quiet, point the pipes straight up at the sky. Turnouts redirect the sound toward Biff and Britany in their McMansion and causes them to shed big crocodile tears at the city council meetings.

 

I was wondering that too. I even went on the Donaldson muffler website and can't seem to find abbreviation to those letters. I don't know if that something Ryder fleet products added on there or what.

 

LR Low-Range
MR Mid-Range
HR High-Range

It's in reference to the Rated Flow CFM (Cubic Feet Minute) of the muffler.

 

That's what I buy from my local NAPA dealer. I have no idea what I paid. I don't pay attention to that very often if they have and I need it that's where I buy it.

 

Thats exactly what i did on my other truck, looked on Walkers website and contacted the Napa dealer that supplied them, called them to verify they had them in stock and purchased them, when i installed them i noticed the megaflow imbedded in the muffler wasn't on them and thought they didn't mark them anymore, in hindsight i think the dealer sold me regular mufflers.

 

All the mega flows I've bought had it embossed up the side. Easy enough to tell just look inside. You can see all the way thru.

 

BS.

 

Low range, mid range and high range what?