- Extensions can be combined with all Junior Starter Sets - Theme sets include cute decorative elements and animal figures to decorate - Ideal extensions for children from 3 years, with many parts GraviTrax Junior is suitable for children from 3 years. Boys and girls build their own ball track worlds, which can be freely supplemented with decorations to build their own themed worlds. With a large number of desert elements and animal figures, children experience the world of the desert up close. All construction and decorative elements are made of wood-bioplastic. Building and playing fun are combined in a unique way! GraviTrax Junior is an interactive ball track system for children from 3 years old. Children can build their own ball track world to their heart's content and can decorate it with all kinds of different theme sets. Creative building and playing fun are combined.