Our manhole includes integral base, risers, top, steps, o-rings, and pipe to manhole connectors as specified. A precast flow channel is available only in the 72" ID Manhole. A transition slab is used when possible to facilitate use of 48" ID cones, and when not possible, our flat top slab is used. Doghouse holes can be formed when it is necessary to drop the manhole over existing pipe. An extended base is also available.