Air stippers vs Shroud

I bought a so-called air stripper and it was marketed as a sound reduction device, and that's what it does. It's on the S510 carbine 

There is a lot of dancing around about what to call these things , LDC for lead dust collector used to be a popular term, wink wink. It's basically like a muffler on your car.

a shroud will extend past the barrel and have equal diameter back to the breech block. An air stripper attaches to the end of the barrel and is sometimes called a pickle.