There are similarities and differences between the two systems. Both systems can be used to maximum invert depth of 600mm. However, the Shallow Inspection Chamber (4D960) has a 250mm diameter, is of one piece construction with one through channel and one inlet each side (supplied blanked off) and has a choice of two lids. Both covers are mechanically air-tight and can therefore be used inside a building.

The Multi-Base system is 300mm diameter and comprises of a choice of 10 bases with raising shafts of 200mm invert. One base plus two shafts equal an invert of 600mm. The cover in this range is NOT a sealed cover and therefore is not suitable for use inside buildings.