Eiffel's Tower Bolt and Brunel's Nut & Bolt Great Minds Puzzles with Bonus Twisted Nails Puzzle Set contains two sturdy nut & bolt disentanglement puzzles. One is a level 1 difficulty, the other is a level 4 difficulty. Remove the washer from the bolt on each puzzle. Sounds easy, but a clever design to these high quality puzzles provide a great challenge. Each puzzle comes individually boxed with solution information included. Also included is the tricky "twisted nail" puzzle as a bonus. Recommended for ages 12 through adult. (some very bright 8 to 11 year olds may also enjoy.