Consisting of 8 pieces of armor it is a fairly complete gear set, while not being an actual set. It alone is not sufficient gear for tanking level 80 heroic content, especially due to it's lack of gem slots. However, it can be used to fill in slots by a fresh tank, and is sufficient for tanking non-heroic Northrend content.
It is important to note that while there are no gem slots, this equipment has higher than normal defense rating stats, though it lacks other avoidance/mitigation, and has less stamina than seen on higher gear. This means that tempered saronite pieces are great for breaking the 535 Defense "soft-cap" of heroics without the necessity of buying gems and enchantments. However, the tank will still be unable to tank heroic content without the health pool available in other gear, and this should only be used to get those last few points of defense, not as a mainstay of your equipment.