... and wood pulp 3. good printing duplex paper board with gray back High quality,low price,fast delivery Good folding strength High ... stiffness duplex paper board with gray back1) A and AB ... produce 250gsm,300gsm,350gsm,400gsm, 450gsm and 500gsm paperboard with grey/white back. 2) Consistent quality 3) High stiffness, excellent print ...