Concentrate

This is a Magus Arcana — a class feature gained through that class's own talent choices, not a feat you pick through normal feat selection.

(Ex) The magus can reroll any concentration check he has just made with a +4 bonus. He must use this ability after the roll is made, but before the roll's outcome is determined. The magus must take the second roll, even if it is worse. The magus can use this ability once per day.