are quite delicate. Don't over tighten as this will readily snap the nozzle in two inconvenient parts. (The video instructions gave the impression I could be a bit firm.) You'll want to find someone infirm to do this business or you'll be left waiting for at least a week or so for replacement parts like myself.
I suggest always follow as a instructions: http://support.zortrax.com/hc/en-us/articles/200986581-Nozzle-replacement
Here in this video version the instructions add teflon tape. As well the amount of force exerted moved the carriage more than I experienced before the nozzle seperated in the extruder.