GraviTrax Bridges ExpansionThe GraviTrax Bridges expansion is a pack that can be combined with the GraviTrax Starter and Pro Set. Create the element of surprise! Bridge track sections! Bypass large gaps with Bridges. Combine the Bridges with your GraviTrax Starter Set for even more variety by interlinking track sections for really spectacular results GraviTrax is a STEM interactive marble run that allows players to design and build tracks, whilst experimenting with gravity,