... , grade B, in sheets, in rolls Duplex board with gray back (grey back): grade A and grade B, 230, 250, 300, 350, 400 ... , 450, 500gsmIt is used for packaging and printing, mainly for cigarettes, medicines, health supplement, wines, facial tissue ... also provide special gsm above 250gsm for both white back and grey back as customer's request. duplex board with gray back