We supply the undensitied silica fume which is a by-product during melting Silicon Metal or Ferro Silicon for long-term, the specifications as follows: SiO2: Customs code: 28112200 Specifications and price: SIO2 contents >85% I.L <7.0% 45μm >90% min Density>600kg/m3 Packing - jumbo bags 900kg/packet or by buyer抯 request. certificate : SGS certificate OR others THEREE:Silicon slag Contents:SI>35-55% SIZE:by buyer抯 request