This is the “Custom Heater Block by Mr Anders Olsson, discussed at large in this tread in the Ultimaker forum.
Installing it lets you change nozzles on the Ultimaker 2 in less than 20 seconds.
“The Olsson Block” ships with one “JET 0,25″JET 0,40″JET 0,80″ nozzle seen in the picture. This nozzle works with your existing configuration right away. Also included are the tools you need. You must also have the UM2 standard tool which came with the printer; the tiny umbraco style “key”.