Granular materials behave like fluids if the packing fraction is low enough. When a steel ball is dropped in a granular bed a jet appears, this is already known from literature. However, this jet doesn’t always appear, for example when the packing fraction is too high. In this research the jet height is measured as function of the packing fraction. A critical packing fraction was observed for which the jet started to appear and for packing fractions lower than the critical packing fraction, the height was quasi linear. Also, the jet height as function of the impact velocity is measured and presented on this website.