high-density medium density and low density sand for exploring more oil and gas. a little investment .much gain ... : 12-18 mesh, 12-20 mesh, 16-20 mesh, 16-30 mesh, 20-40 mesh between 30-50 mesh, 40-60 mesh, 40-70 mesh and so on ... maintain the high conductivity of oil and gas. 40-70 mesh ceramic sands for oil and gas wells