Grades 1 & up. Equip children with the tools they need to build the world they want! These dynamic modeling systems introduce mathematical foundations and encourage logic and problem solving. Each set provides a rich and rewarding STEM experience, and with no additional tools required, budding engineers are ready to create and build different structures. Sets are based on the Pratt scale standard unit blocks, and each set comes with a built-in storage case that features construction ideas. Bridge Builder includes 620 mini unit beams in 15 different shapes and 19 hardwood mini unit bricks. Crane Builder includes 175 mini unit beams in 15 different shapes and 3 hardwood mini unit bricks.