As an interactive game, puzzles are a fun way to promote important cognitive skills through hands-on learning. Puzzles are perfect for solving alone or in a group. 4in1 Puzzle Set. Size of the completed puzzle: 28.5 x 20.5 cm. A set of four puzzles with 12, 15, 20, and 24 pieces is a great way to have fun while simultaneously improving the ability to assemble more and more pieces together.