... be nice,.smooth , good elastic curve , no distort ,easy to open, the cover should not be sprayed on ... , durableApplications:1,Molded resin covers, composite materials SMC covers , composite material BMC covers, magnesium covers, resin covers, polymer covers ... pipe well, heat supplied, gas well4,Round SMC Manhole Cover&Circle BMC manhole covers&resin fiberglass covers&Molded resin covers&molded ...