Designed by Anders Olsson, this block allows you to easily change nozzles. A .4mm nozzle is included. Block is designed only for Ultimaker 2 and 3mm filament (not 1.75mm filament).
Block also has access such that you can PUSH out heater or temp sensor if you need to change anything.
Standard threading such that it will work with any e3d v6 3mm nozzles which can be purchased separately (if you want to pay more money) at printedSolid.com (they cost more at those stores but those stores have other sizes to choose from).