This is a useful nozzle wrench for mk10 extruders. it's practical when you don't have any actual wrench.
Heater neither have to be turned on nor warm while using the tool, nozzle can be unscrewed cold as long as there's no loaded filament. Ptfe tube prevents the filament from sticking so there's no problem, plastic can be removed once you have taken the nozzle apart.
over 50% (for a stronger part)
it has tolerance to ensure it fits or if you have solidworks 2017 you can change that measure