This blue-emitting plastic scintillator contains natural boron at concentrations up to 5% by weight. It is a clear, stable plastic with physical properties similar to those of the standard Eljen plastic scintillators. Its principal applications are fast neutron spectrometry and thermal neutron detection. The primary function of the boron is to provide a unique scintillation signal for low energy neutrons. The standard formulation contains 5% boron, and practical boron concentrations down to 1% are available.