This set from Learning Resources is a great tool for early STEM learning as kids create 5 separate simple machine designs!
Characteristics: Set features everything needed to build 5 simple machines: lever, pulley, inclined plane, wheel/axel, and wedge. Machines can be further modified with 4 included weights (5 grams and 10 grams) and 8 rubber-bands to make alterations to effort, force, load, motion and distance. 63 pieces total, labeled for easily assembly, separation and storage. Activity guide included.
Size: 14 1/2 x 9 1/2 x 4 1/3 inches
Age: 8 years and up