2nd stage vs octo

[mupwi]

hi could somone on here explane the difrence between these two I am mainly a freediver and am looking to get into scuba just been looking at the cost of gear and courses from what I reed they apear to be the same thing but have vastly difrent prices your coments would be much apreciated

[salibandy]

Second stages regulate the pressure of air so that it's suitable to breathe. Your primary regulator is a second stage, and so is your octopus. The octopus is your secondary regulator, a spare in case your primary fails. Usually the octopus is a lower quality version of the primary reg, if it's the same model.