ECR4Kids Criss-Cross Connector Math Manipulatives Building Kit, Educational Sensory Learning Toys for Children (400-Piece Set) Kids' Building Kit Criss-cross connectors includes 400 math manipulative pieces to help toddlers learn math skills while sorting, counting, designing, and constructing STEAM Approved  playing with manipulatives enhances S.T.E.A.M. education (Science, Technology, Engineering, Art and Mathematics), which emphasizes teaching subjects that have real-world applications Brain-Boosting Fun  enhance fine motor skills, hand-eye coordination, spatial reasoning, problem-solving, cognitive ability, pretend play, counting and early math, creativity and imagination Easy-Snap Connection  kid-friendly pieces are designed to be easy for children ages 3 and older to snap together and take apart Storage Container  comes in a durable clear plastic bin with a locking lid and easy-to-carry handle for quick clean up; bin dimensions 15.5 L x 11 W x 6 H