The standard knob of Ultimaker did not really appeal to me because it was relatively difficult, e.g. to set the temperatures from 0 to 240 ° C. With this rotary knob you can enter such values quickly. Update 05.02.2017: Increase the outside diameter of the knob by 1.50 mm. Acceleration of the printing process. Removing the existing rotary knob from Ultimaker: Behind the existing rotary knob of Ultimaker there is a transparent protective housing, which is illuminated by the LED's. At the rear of the protective housing there is a small opening. With a screwdriver you can push the knob of the potentiometer through the opening. But be careful, do not use a lot of pressure! I have uploaded new pictures, which clarify the process. Sorry for my bad English.