Improved Concussive Shot

From wow.incgamers.com

Talent: Improved Concussive Shot
Effect: Gives your Concussive Shot a % chance to stun the target for 3 sec.
Statistics: Rank 1 = 4%, Rank 2 = 8%, Rank 3 = 12%, Rank 4 = 16%, Rank 5 = 20%.