This is one piece of the complete entry-level tanking Cobalt set. Each item is made by Blacksmiths, mats are dirt-cheap, and recipes are trained starting at 360 to 375 for the chest piece. Level requirement for all is 70.
The complete set provides:
310 Defense Rating
Everything but the shield (for DKs) provides:
288 Defense Rating
Cobalt Triangle Shield
Once you hit 74, you'll want to start trading in for the Tempered Saronite pieces.
Check here for more info on the Tempered Saronite gear.