GraviTrax PRO Add on MixerThe GraviTrax PRO Add on Mixer is an expansion item that can be combined with the GraviTrax Pro Set. Mix up the marbles journey with the Mixer. Add some surprise to your tracks by sending up to three marbles into the Mixer and see which sides they exit from GraviTrax is a STEM interactive marble run that allows players to design and build tracks, whilst experimenting with gravity, magnetism and kinetics to explore endless possibilities and infinite