Quoted from FMF's web site:
"Gnarly
The FMF Gnarly pipe focuses on increasing the lower RPM horsepower and torque to get you out of the toughest terrain. When looking to add 4-stroke tractor like torque to your 2-stroke and you need a pipe to withstand the harsh elements, this is the pipe for you.
Nickel plating is an FMF trademark and has been ?copied? by everyone making it the most imitated expansion chamber in the world.
Super strong 18 gauge steel construction makes it GNARLY!"
18 gauge steel is .048