ductile iron manhole cover 1)specs:QT500/7 2)ISO9001:2000 3)cofirm to EN124 standard 4)class: B125 1), Ductile iron manhole cover made by Xinxing Pipe Fittings Co., Ltdstrictly conform to standard & are free from sand hole.2), Smooth and free from sand holes, blow holes, distortion or any other defects3), Processes:a) Automatic machine linesb) Moulding boardsc) Green sand with hand moulding4), ...