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Delrin balls are used for the eyeballs and come in multiple sizes, which is helpful when first determining the perfect size against the sculpted head. Once a size is chosen, silicone molds are made of the delrin balls. After plastic is poured and cured in the molds, they are sanded and machine drilled to create a space for the iris and pupil, which is then painted. The holes are filled by filling the same molds from earlier with clear urethane and placing the balls back into the mold. Since the urethane has to cure without bubbles, the molds are placed in a pressure pot while they cure. Finally, a small pinpoint hole is drilled into the front of the eye so that the animators can move the eye with a needle during animation.