1.20/40 high grade proppant sand 2.High crushing strength 3.Increase output of ... %-50% 4.supplier of sinopec and petrochina 20/40 high grade proppant sand Intertek Refractories Co., Gongyi City, founded in 2001 ... a high-density, medium density, low density and many other series of ceramic products, covering 20/40 mesh, 40/70 mesh ...