Build your own hydraulic Robotic Arm! Fun & easy to construct for children & 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 & rotate 90°. Made from die-cut plywood, the frame is precisely cut & can be assembled in 1-2 hours. Standing at 37cm high, & stretching up to 49cm, the hydraulic arm needs no battery, simply add water to put it to the test!