Drain Board is molded by PP&HDPE with high strength , the compressive strength is extremely high and doesn't distort or burst. Product Uses Roof garden drain,draining for roof and wall,paved areas and roadways,sport fields ,drain basement walls ,pond filtration ,bridge abutments ,tunnels and landfills ,golf courses drain.DRAIN BOARD500*500*30 Material composition100% recycled PPcolourBlackSurface void area60%Internal void area88%Weight capacityAbove 100ton/m2Compressive strengthMax.900KN/M2Discharge capacity@1% gradient700L/m2.s