Building Blocks, set of 4. The Red block measures 1 1/4" x 5/8" x 1/2", the Blue block measures 1" x 5/8" x 1/2", the White block measures 5/16" x 1 1/4" x 1/2", and the Yellow block measures 5/8" x 5/8" x 1/2". These blocks do not stack onto one another because the bottom of each block is smooth, not dimpled.