Grimm's Building Set Sloping BlocksTricky building set with different tilted blocks. Only the matching colours will complete a rectangle. All 6 blocks within one shade of colour (blue red green yellow and purple) have the same tilt angle and therefore will also complete a rectangle. By building and playing with the uneven blocks, children develop fine motor skills and spatial thinking skills. 30 buidling blocks in a wooden frame. Materials: lime wood, non toxic water based color stain