3 X 3 X 3 Concave Rubik Cube Is The Combination Puzzle. This Cube Is Fast With Excellent Corner, This Is Very Flexible And Very Smooth To Rotate. It Helps To Improve The Hand Eye Coordination, Mathematical And Logical Thinking. This Cube Is A Brain Teaser Which Improves Cognition Performances, Enriches Observation, Coordination And Recognition Agility. This Cube Puzzle Helps To Increase The Thinking Power And Develops Intentional Mindset.