We are proposing to accurately map out the crystal electric field (CEF) levels in NdB4, ErB4 and HoB4 using MARI. These compounds belong to a family, REB4, which is a rare experimental realisation of the Shastry-Sutherland lattice. Despite the CEF interactions having considerable influence on the magnetic properties, very little work has been done to investigate the CEF interactions. We will produce powdered samples of ErB4, NdB4 and HoB4 and have grown single crystals, which we have characterised. These have shown interesting behaviour such as fractional magnetisation plateaux and complex phase diagrams. While neutron experiments we have performed on NdB4 and HoB4 have also shown some intriguing results.