2012 Airborne Guardian.
The hub shell is aluminum, and the free-hub driver body (the part that that cassette goes onto), is steel. Thanks~
Please Note: I no longer work for Airborne as of 12/5/2014. If you have an Airborne question please contact them directly.
Thanx J! I'm going SS. Didn't want to get a cheap cog if it wouldn't handle it.