18 months and up. Integrate early Stem learning into playtime with the Twisty Tools Nuts and Bolts Set. This set comes with 84 pieces that children can connect to one another in lots of interesting ways. To fit the nuts onto the bolts, children must figure out which nuts and bolts have matching patterns and designs. This quest will strengthen children s matching skills, shape recognition skills, and pattern recognition skills. Largest piece measures 1.7"L x 4"W. Smallest piece measures 1.5"L x 1.5"W x .8"H.