But there are also some around 550MM, but the commonly used ones are still the 600MM type. The 700MM size is for clearing purposes. Cast iron manhole covers are generally divided into round and square shapes, according to international standards.

This varies by north-south differences, not just one type. In terms of urban road administration.

800B125 and so on. Cast iron manhole cover specifications: heavy-duty 400, general type 250, light 125, different sizes. 700MM. If less than this specification, there is a type of well called a inspection well, 400*700B250.