Mage · Frost · tier 1 · from level 10
Improved Frostbolt
+30.9 Frostbolt
5/5 · level 60 · per second of casting
Improved Frostbolt
Rank 5/5
Reduces the casting time of your Frostbolt spell by 0.5 sec.
Averages, counting crits and misses, for a level 60 Mage with a typical weapon and no other gear or buffs, against a target your level. Worked out from the game's own data, the same way as the Foresight addon.