With Control of Error Designed In the Blocks are an attractive addition to the Montessori Classroom. 12 beech wood blocks in a cotton bag. Two in each colour: red, blue, green, yellow, orange, violet (40 x 40 x 40 mm). The blocks are hollow and filled with resonating bodies of which matching colour pairs make identical sounds.
If, for instance, a blind-folded child can match the pairs correctly by ear, he or she can check the result visually. If they match in colour they have been matched correctly in sound.