This building block set contains 24 U-shaped wooden blocks - four of each in six different colors. Their unique shape makes the blocks easy to grasp and helps them lock together if desired. Building anything from simple flat designs to high towers is fun and challenging while developing gross and fine motor skills, balance and design. The blocks measure 7 x 3.5 x 2 cm (about 2.75 x 1.5 x 0.75"), are made of tough, sustainably-harvested rubberwood and are colored with non-toxic water-based stains that will not chip, flake or fade. The set comes in a storage tray measuring 24 x 17 cm (about 9.5 x 6.5").