Didax Unifix Cubes are educator developed, classroom tested, and always trusted for efficacy, durability, and authentic learning value - These math manipulatives can be used in conjunction with the full line of other Unifix products built to extend learning comprehension skills, which consists of interlocking cubes which is an excellent visual aid for counting, measurement, and addition. Built from soft pliable material these single – direction linking cubes are great for small hands, maintain linking connections over years of use and help students focus on the activity of learning, it's why they are the #1 brand of linking cubes