Pros:-Great idea for a toy that teaches math! The idea is in the spirit on Montessori counting rods (check those out too!). There are 12 rods/blocks ranging from 1-12 inches tall; each features a different animal. My son loves to add up two animals to get the third one. At age 3, he uses included notebook with tasks independently (by himself) and even scribbles appropriate numbers in the notebook. This is one of the toys that he picks up and works with by himself:).Cons:-Upon opening the box there was a strong smell like that of some markers, or glue?. Blocks did not smell, just the box, maybe it was the marker that was included in the box. The blocks are made in China.-Blocks came with some small defects in paint and the edges chip off paint very fast. The paint cover is glossy like that on Thomas and Friends wooden locomotives, but chips much easier.-On one side of the block, there are little stripes marking the inches like on the ruler, but without numbers. My son counts the stripes and there is always one two many (he does not know that you don't count the first one). It would be better if one-inch intervals were indicated with alternating colors as in Montessori counting rods.Otherwise, perfect toy and learning material.