Arcane Concentration

From wow.incgamers.com

Talent: Arcane Concentration
Effect: Gives you a % chance of entering a Clearcasting state after any damage spell hits a target. The Clearcasting state reduces the mana cost of your next damage spell by 100%.
Statistics: Rank 1 = 2%, Rank 2 = 4%, Rank 3 = 6%, Rank 4 = 8%, Rank 5 = 10%.