Stimulate your child's developing mind and channel their creativity with Geomag MASTERBOX PRO-L 388 piece magnetic construction set. Your little engineer-in-the-making will gain the tools to build architecturally sound structures like a bridge using panels, magnetic rods, and non-magnetic steel spheres. With a little imagination, they can build something more fantastical and abstract! This STEM.org certified toy is designed to help children develop hand/eye coordination, motor skills, problem solving, and visualization through the science of magnetic construction. PRO L magnets are 30%+ stronger than our classic line allowing for larger creations. STEM.org certified toy that helps in the development of creativity, fine motor skills in addition to stimulating imaginative play and curiosity through the science of magnetic construction. Geomag