It's resistance. All the elemental symbols on items indicate resistance.
For most elements, the resistance added by items is insignificant compared to the Bar-Element spells, but because there isn't a Barlight or Bardark, resistance to those two elements is slightly more important on items than the other.
Still, IMHO, not worth worrying about too much, unless you make a habit of hunting elementals.
I'm probably just an idiot though, and have forgotten the price. I'll edit, or something..with the correct price. After this damn maintenance is over >.>
Although it may be expensive, around 3k in Fairy (don't recall exact price), they are worth it. Especially at low levels when you have little MP and you are a mage. I'm a black mage and I think of using them until I get Morrion Earrings...when I get rich ¬¬