Núm vặn trục D 6mm (6mm D shaft knob)

these knobs were made to replace the knob on an electric kettle but should fit many other applications. The knob itself it printed in TPU. you could print in other materials but you may need to scale slightly for the D shaft to fit, in TPU it has a nice friction fit on the shaft. 

One of the models included has a hole for a pointer / indicator. The pointer can be printed in anything and is made to be split in colors at a layer line to create the red line shown in the first image.