Pokémon breeding/Games/How to breed/Inheriting stats/Generation VI

From onward, if at least one parent holds a Destiny Knot, the baby will inherit five IVs instead of three.

This can be combined with an EV-enhancing item to ensure that one desired IV is always inherited; however, the offspring will still inherit only a total of five IVs from its parents (the EV-enhancing item simply guarantees which IV will be transferred for one of the five that the Destiny Knot allows).