The Nozzle Mk8 represents an improvement over the previously used Mk7. The main difference between the MK8 Stepstruder and the MK7 is the ratio of molten and unmelted plastic inside the heated nozzle. You do not want the PLA to remain melted for too long, as it will start to degrade, but the new design should eliminate this problem. About the same amount of plastic enters each nozzle, but in the MK8 nozzle, more of this plastic remains solid. This means that any piece of PLA will spend less time sitting in the heated liquid nozzle and will not have much time to degrade.
