Unit Bricks 620 PCS Bridge Building Classroom Kit - STEM Learning Toy for with Instruction Manual

Do not buy this product. It is a poorly designed waste of good plastic. I am a structural engineer. I bought this building set intending to teach my grandchildren about basic engineering principles. I tried building it myself before working with my grandchildren. After 15 minutes of "play", I found it is a complete waste of time. I returned it.The instructions/plans are written poorly. It does not model in any way the structure of a real bridge. The joint system is a bad design. The joints do not stay together with even the slightest tension.If one of my engineers designed this product, I'd fire him.