Complex sentence: When added to a combination, with his brother GaoPolar Double Knuckle (ダブルナックル "Daburu Nakkuru") is added to that formation's name, or Knuckle in Episode 38 when GaoBear was added alone with GaoKing.
Split into simpler sentences: When added to a combination with GaoPolar, is added to that formation's name. If only one is used, Knuckle is added, as seen in episode 38 when GaoBear was added alone with GaoKing.