The Learning Resources STEM Explorers Machine Makers is an engaging and educational STEM building toy. With 9 STEM challenges, kids can learn the science behind real-world machines as they build their own creations. This 50-piece set includes gears, pulleys, belt drives, and connectors, allowing kids to explore and understand mechanical principles. The set also comes with 10 activity cards packed with challenges to further enhance critical thinking and problem-solving skills. Additionally, the STEM Explorers Machine Makers set is compatible with other Gears! Gears! Gears! sets for even more building fun. It's the perfect way to introduce children to the exciting world of STEM - Science, Technology, Engineering, and Mathematics.