The study of the operational space of plasmas with Type III ELMs, in terms of local and global plasma parameters, in JET Mark II Gas Box (GB) divertor was described. The Type III ELMs were observed in standard ELMy H-modes and in plasmas with an internal transport barrier (ITB). In JET Type III ELMy H-modes, the energy confinement enhancement factor degraded with density and increased with triangularity over the entire collisionality range. It was observed that the classical pedestal temperature for the transition from Type III to Type I ELMs was increased with decreasing density at low density and was approximately constant at high density.