... many colors beautify the environment.3. Light WeightIt weight only 1/3 of cast-iron manhole cover, more expediently transport, install, and ... Black Hole accident.5. Climatic resistantIt uses big molecular weight and chemical steady macromolecule complex material, adopts scientist prescription, ... cover and its under. It gets over the problem of cast-iron and cement manhole cover run, jump, sound. It ...