Build your own hydraulic Robotic Arm! Fun and easy to construct for children and adults alike; this 3 dimensional model is a great demonstration of a hydraulic power system! The arm function uses some of the same principles that drive real world machines; it can lift small items horizontally and rotate 90 Degree. Made from die-cut plywood, the frame is precisely cut and can be assembled in 1-2 hours. Standing at 14-inches high, and stretching up to 19-inches, the hydraulic arm needs no battery, simply add water to put it to the test!.