Identify the top manhole covers? Identify no futher then Tradersfind. It is made with different materials such as cast iron, ductile iron, concrete and in some cases, with glass reinforced plastic (GRP) and It is essential to ensure that the cover does not get dislodged by pressure from gasses released in the drains and also from sucking pressure of fast moving vehicles.Tradersfind... https://www.tradersfind.com/search/manhole-covers