This is a unit that allows space for a pedestal.  Other types are designed for single pipe work or half  depth pedestals.  My assumption is that if it is designed for the whole length pedestal it would be a universal size at the back hence I was looking at the overall dimensions when ordering.  After several hours putting it together I found that this one has an extra narrow space for  the pedestal.  Shame because the unit is quite nice, easy assembly instructions.  I now have to find a jig saw to attack the unit to cut out a big enough space at the back!!   I note several other reviewers have had this issue as well.