The casing spool has a top bowl to accommodate the casing hanger. The spool also has a bottom 
  bowl with a packoff seal and a flange 
  or clamp hub for mounting it on top of a casing head or previous spool. Outlets are provided 
  for annular access. Multiple casing spools may be 
  stacked to hang intermediate and production casing strings.
  Outlets: Line pipe outlets & Studded side outlets