... kit, including front and back lids, including assembly notes. EMS xxx 3unit:base rack, useable height= 3 units (132mm) EMS ... xxx 6unit:base rack, useable height= 6 units (264mm) EMS xxx 9unit:base rack, useable height= 9 ... units (396mm) EMS xxx 12unit:base rack, useable height= 12 units (528mm)EXTENTION KITS: ...