Our manhole includes integral base, risers, top, steps, butyl mastic, pipe to manhole connectors as specified, and in some cases, a precast flow channel. A transition slab is used when possible to facilitate use of 48" ID cones with o-rings, 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. One limitation to sanitary square-wall manholes is that the pipe cannot be angled in relation to the structure wall. If an angle is necessary, a custom box must be designed.