Klutz prevents the use of any held items in battle. It does not affect the item effects like prize money, experience, effort values or friendship. The user cannot use Fling but, when consuming a berry via Bug Bite or Pluck, the effects of the berry will affect the attacker. For moves that change with held item like Judgement or Techno Blast, it will turn into a Normal attack. Klutz does not affect Mega Stones or Z-Crystals or prevent Primal Reversion.