These extra large building blocks promote creativity, logic and reasoning skills as well as developing motor skills and hand/eye coordination. Blocks interlock securely and encourage children to work and communicate together. Gorilla Blocks foam evolved from automotive safety applications, and is extremely durable, non-toxic, weatherproof and recyclable. Set includes 66 pieces in assorted sizes and colors. The entire set weighs only 8 lbs., but each individual block can hold up to 220 lbs. of weight.