Nozzle size indicator

Designed to fit to the acrylic frame of the Prusa i3 Pro B.
It allows to not forget which nozzle diameter is mounted on the printer.
No need for glue or whatever. You'll just have to change the PLA's color when it will start tho print the numbers.

Here is the G-code that you have to insert in Slic3r, tab "Printer settings", field "Before layer change G-code":
{if [layer_num] == 16}M600 X30 Y30 Z10 E3 L0; X[pos] Y[pos] Z[relative lift] E[initial retract] L[later retract distance for removal]
In this example here above, 16 is the old layer with the old color. That means layer 17 will have the new color.

I've added the possibility to mount 2 pressure screws in the back, but honestly this is not needed, this Thing fits perfectly to the acrylic frame which is 8 mm thick.