Toyota Repair: 2004 4runner rear shock, rear shocks, rear shock

Question
I have a 2004 4WD 4runner sport.  I need to replace the rear shocks but there is a hose that is connected to the shocks and I don't know what it is for.  I don't have air or hydrolic shocks. Any ideas?

Answer
Some 4-Runners have ride height control, there is a control switch for this on the dash, the shocks have to be the exact replacement from the toyota dealer and it would require a technician to install them following the instructions in the factory repair manual.